If I understand correctly your two points, they can be worded as follows
- Because there was an Old Covenant, there is no need to be saved by confessing faith in Jesus Christ, and Christianity is unnecessary.
- Since God is infallible and perfect, doing nothing unnecessary, assuming that point 1 is true, then Christianity cannot have been created by God.
For reference, I will be using the ESV translation.
Following the logic you have presented, Christianity is either created by human means or Satanic means, and Jesus, its founder, is either insane, a liar, or Satan himself. Rather than attempt to restate what has already been stated well, C.S. Lewis in his book, "Mere Christianity", debunked that notion. You can see the relevant excerpts at Is C.S. Lewis’s Liar-Lord-or-Lunatic Argument Unsound?
As additional support, The Mathematical Probability that Jesus is the Christ has some helpful statistics about Jesus, who fulfilled many, many prophecies.
So, if we are starting from the angle that Jesus is God, then the answer becomes very simple,
John 14:1-7 ESV
1 1 Let not your hearts be troubled. Believe in God; believe also in me. 2 In my Father's house are many rooms. If it were not so, would I have told you that I go to prepare a place for you? 3 And if I go and prepare a place for you, I will come again and will take you to myself, that where I am you may be also. 4 And you know the way to where I am going.” 5 Thomas said to him, “Lord, we do not know where you are going. How can we know the way?” 6 Jesus said to him, “I am the way, and the truth, and the life. No one comes to the Father except through me. 7 If you had known me, you would have known my Father also. From now on you do know him and have seen him.
That is quite conclusive, so long as you take Jesus' word as God's word. If you don't, well, that's what the other parts of this answer is for.
Jeremiah 14:20 ESV
We acknowledge our wickedness, O LORD, and the iniquity of our fathers, for we have sinned against you.
Job 15:14 ESV
What is man, that he can be pure? Or he who is born of a woman, that he can be righteous?"
From these verses, we find in the Old Testament that humanity needs to be atoned for, which God implements the sacrificial system in Leviticus to temporarily solve:
Leviticus 4:1-3 ESV
1 And the Lord spoke to Moses, saying, 2 “Speak to the people of Israel, saying, If anyone sins unintentionally in any of the Lord's commandments about things not to be done, and does any one of them, 3 if it is the anointed priest who sins, thus bringing guilt on the people, then he shall offer for the sin that he has committed a bull from the herd without blemish to the Lord for a sin offering.
The verses following Leviticus 4:1-3 go into further detail about the sacrifices necessary for atonement.
Yet, your question is actually well addressed in the book of Hebrews, which specifically talks about the Levitical law, and why Jesus was needed to save us:
Hebrews 7:11-28 ESV
11 Now if perfection had been attainable through the Levitical priesthood (for under it the people received the law), what further need would there have been for another priest to arise after the order of Melchizedek, rather than one named after the order of Aaron? 12 For when there is a change in the priesthood, there is necessarily a change in the law as well. 13 For the one of whom these things are spoken belonged to another tribe, from which no one has ever served at the altar. 14 For it is evident that our Lord was descended from Judah, and in connection with that tribe Moses said nothing about priests.
15 This becomes even more evident when another priest arises in the likeness of Melchizedek, 16 who has become a priest, not on the basis of a legal requirement concerning bodily descent, but by the power of an indestructible life. 17 For it is witnessed of him, “You are a priest forever, after the order of Melchizedek.”
18 For on the one hand, a former commandment is set aside because of its weakness and uselessness 19 (for the law made nothing perfect); but on the other hand, a better hope is introduced, through which we draw near to God.
20 And it was not without an oath. For those who formerly became priests were made such without an oath, 21 but this one was made a priest with an oath by the one who said to him: “The Lord has sworn and will not change his mind, ‘You are a priest forever.’”
22 This makes Jesus the guarantor of a better covenant.
23 The former priests were many in number, because they were prevented by death from continuing in office, 24 but he holds his priesthood permanently, because he continues forever. 25 Consequently, he is able to save to the uttermost those who draw near to God through him, since he always lives to make intercession for them.
26 For it was indeed fitting that we should have such a high priest, holy, innocent, unstained, separated from sinners, and exalted above the heavens. 27 He has no need, like those high priests, to offer sacrifices daily, first for his own sins and then for those of the people, since he did this once for all when he offered up himself. 28 For the law appoints men in their weakness as high priests, but the word of the oath, which came later than the law, appoints a Son who has been made perfect forever.
On top of that,
Hebrews 9:11-28 ESV
11 But when Christ appeared as a high priest of the good things that have come, then through the greater and more perfect tent (not made with hands, that is, not of this creation) 12 he entered once for all into the holy places, not by means of the blood of goats and calves but by means of his own blood, thus securing an eternal redemption. 13 For if the blood of goats and bulls, and the sprinkling of defiled persons with the ashes of a heifer, sanctify for the purification of the flesh, 14 how much more will the blood of Christ, who through the eternal Spirit offered himself without blemish to God, purify our conscience from dead works to serve the living God.
15 Therefore he is the mediator of a new covenant, so that those who are called may receive the promised eternal inheritance, since a death has occurred that redeems them from the transgressions committed under the first covenant. 16 For where a will is involved, the death of the one who made it must be established. 17 For a will takes effect only at death, since it is not in force as long as the one who made it is alive. 18 Therefore not even the first covenant was inaugurated without blood. 19 For when every commandment of the law had been declared by Moses to all the people, he took the blood of calves and goats, with water and scarlet wool and hyssop, and sprinkled both the book itself and all the people, 20 saying, “This is the blood of the covenant that God commanded for you.” 21 And in the same way he sprinkled with the blood both the tent and all the vessels used in worship. 22 Indeed, under the law almost everything is purified with blood, and without the shedding of blood there is no forgiveness of sins.
23 Thus it was necessary for the copies of the heavenly things to be purified with these rites, but the heavenly things themselves with better sacrifices than these. 24 For Christ has entered, not into holy places made with hands, which are copies of the true things, but into heaven itself, now to appear in the presence of God on our behalf. 25 Nor was it to offer himself repeatedly, as the high priest enters the holy places every year with blood not his own, 26 for then he would have had to suffer repeatedly since the foundation of the world. But as it is, he has appeared once for all at the end of the ages to put away sin by the sacrifice of himself. 27 And just as it is appointed for man to die once, and after that comes judgment, 28 so Christ, having been offered once to bear the sins of many, will appear a second time, not to deal with sin but to save those who are eagerly waiting for him.
Hebrews 10:1-18 ESV
1 For since the law has but a shadow of the good things to come instead of the true form of these realities, it can never, by the same sacrifices that are continually offered every year, make perfect those who draw near. 2 Otherwise, would they not have ceased to be offered, since the worshipers, having once been cleansed, would no longer have any consciousness of sins? 3 But in these sacrifices there is a reminder of sins every year. 4 For it is impossible for the blood of bulls and goats to take away sins.
5 Consequently, when Christ came into the world, he said, “Sacrifices and offerings you have not desired, but a body have you prepared for me; 6 in burnt offerings and sin offerings you have taken no pleasure. 7 Then I said, ‘Behold, I have come to do your will, O God, as it is written of me in the scroll of the book.’”
8 When he said above, “You have neither desired nor taken pleasure in sacrifices and offerings and burnt offerings and sin offerings” (these are offered according to the law), 9 then he added, “Behold, I have come to do your will.” He does away with the first in order to establish the second. 10 And by that will we have been sanctified through the offering of the body of Jesus Christ once for all.
11 And every priest stands daily at his service, offering repeatedly the same sacrifices, which can never take away sins. 12 But when Christ had offered for all time a single sacrifice for sins, he sat down at the right hand of God, 13 waiting from that time until his enemies should be made a footstool for his feet. 14 For by a single offering he has perfected for all time those who are being sanctified.
15 And the Holy Spirit also bears witness to us; for after saying, >sup>16 “This is the covenant that I will make with them after those days, declares the Lord: I will put my laws on their hearts, and write them on their minds,”
17 then he adds,
“I will remember their sins and their lawless deeds no more.”
18 Where there is forgiveness of these, there is no longer any offering for sin.
That should address your second point. As for your first, that will be addressed in the third and final part, which is thankfully not necessary to be very long.
Hebrews 11:1-2 ESV
1 Now faith is the assurance of things hoped for, the conviction of things not seen. 2 For by it the people of old received their commendation.
This verse, along with the previous section, should address the first point.
- Jesus is the Christ (Part 1)
- Humans are separated from God, and need atonement (Part 2)
- Atonement can only come through blood
- Jesus died to provide that sacrifice eternally, for all who would receive it, past, present, and future (Part 2)
- Before the New Covenant, even before the Old, people were saved not necessarily by sacrifices, but by their faith in God. Now, however, is the New Covenant, which explicitly has put Jesus as the only Way, the only Truth, and the only Life, outside of which no one can reach the Father. I can't claim to know exactly how that works, but thems the words of God, so thems the truths.
Hope this helps. Pray about it, read the scripture, and seek the Holy Spirit's guidance and voice. If you still have questions, then feel free to ask; just don't exclude God from answering your questions, because He'll do a lot better job than anyone on this website can, me included. Plus, human reasoning won't always connect directly to God, or else faith wouldn't even be necessary. That's part of the reason why I find apologetics kind of a dead-end pursuit, but we do need to have a reason for the hope you have.