The creeds served various purposes. They corrected various heresies that had arisen at the time. The Nicene Creed was written to confront and expose the Arian heresy. This heresy denied the deity of Jesus Christ. The Jehovah Witnesses are "Arians" who deny the deity of Jesus Christ.
The creeds also serve to identify what essential doctrines are as opposed to peripheral points or issues. One's salvation is not based on when Jesus Christ is returning for His church. One's salvation is based on the fact that Jesus Christ is God, this is an essential truth.
You should also know that the creeds are based on the Bible and of course they do not supercede scripture and they are not scripture. In fact, the Bible itself contains "creeds." The Shema/Deuteronomy 6:4 is an expression of the uniqueness and unity of God.
1 Corinthians 15:3-4 is a creed where the Apostle Paul capsulizes the gospel. So is 1 Timothy 2:5-6. I purposefully did not quote the verses so you could look them up and see for yourself. In short, they are a guide for the church in affirming doctrinal truth, refuting error, and encouraging doctrinal instruction.
Now, regarding what you said about Jesus Christ not being equal to His Father. The Jews accused Jesus Christ of blasphemy for being equal to His Father. Just read John 5:17,18, John 8:57-59, John 10:30 through 37, John 19:7 and the complete trial record at Matthew 26:57-68.
Please take note of John 5:18, "For this cause therefore the Jews were seeking all the more to kill Him, because (or why?) He not only was breaking the Sabbath, but also was calling God His own Father, MAKING HIMSELF EQUAL WITH GOD."
Finally, the reason Jesus Christ submitted Himself and was subservient to His Father was because He took the form of a bond-servant/man. This is clearly explained at Philippians 2:5-10. Jesus Christ, who existed as God the Son emptied Himself and took the form of a servant/man. In doing that He laid aside His glory with the Father "BEFORE THE WORLD WAS" (John 17:5) to die for the sins of the world. After His ascension He returned to His original state of glory He already had in the first place.
I want to address John 10:30 where Jesus says literally, I and the Father We are one." According to the context Jesus had just stated that the sheep are equally safe in His hand and in His Father's hand. The power of the Son is equal to that of the Father. It also goes without saying that the Son and the Father are one in purpose.
There is much more at work here because the word "one" (hen) is a neuter number to indicate equality of essence, attributes, design, will and work. Jesus distinguishes the "I" from the "Father" and uses the plural verb "are" denoting "we are." Thus asserts their unity of essence or nature as identical. The Jews knew exactly what Jesus had said and that's why they said at John 10:33, "The Jews answered Him, "For a good work we do not stone You, but for blasphemy; and because You being a man make yourself out God." If you want I can also address why Jesus Christ brought up Psalm 82:6 from John 10:34-38.