Perhaps it is because of this confusion that you describe that your title and body do not really seem to match. I will try to clear up this confusion and answer your underlying question.
The question seems to be: "Why are Christians not more concerned with ritual and seem so divided on what they should do as Christians? Why are they so different from the Jews and Muslims?"
First, the reason there are so many denominations is because of the vast differences in opinions on what those rules are. Why there are so many opinions in Christianity is more of a History/Sociology question.
The Reformation, which brought around the pull from Catholicism and the advent of Protestantism, was also somewhat accompanied by the advent of modern democracy. The first was a pull from the "king" of religion and the second was a pull from the king of the nation. Both occurred in Christian dominated countries. Both are largely responsible for forging the concept that personal opinion is just as valuable as the sovereign's. The effect in Christianity is similar to the effect in politics: numerous opinions and little to no unity.
The question of Christianity having a "sacred" language is that it does. It is Latin. It wasn't until John Wycliffe (1500's) that the Bible was made publicly available in other languages (most notably was English). Before then, Latin was the official language of Christendom, which was widely ruled by Catholicism and the Pope. Why Latin was used so heavily by the Catholic Church is really another question. Also, why Greek or Aramaic is not used today a a bit of another question, however, today, because of the vast number of manuscripts found to date, many scholars actually do turn to the Greek regularly for answers.
But then, why would the average "John Christian" not learn Greek so he could readily turn to it? That is because Christianity is the religion for all. The general message is that all may come as they are and be saved. Many argue that all the Scripture teaches is that you are completely willing to follow God.
First comes faith; then comes practice.
17 ... faith by itself, if it is not accompanied by action, is dead.
20 You foolish person, do you want evidence that faith without deeds is useless[d]? 21 Was not our father Abraham considered righteous for what he did when he offered his son Isaac on the altar? 22 You see that his faith and his actions were working together, and his faith was made complete by what he did. 23 And the scripture was fulfilled that says, “Abraham believed God, and it was credited to him as righteousness,”[e] and he was called God’s friend. 24 You see that a person is considered righteous by what they do and not by faith alone. James 2 NIV
The verse in James, whose meaning is much argued, describes a clear sequence: Faith brings deeds which brings righteousness. The message is that when you fully submit your life to God and "believe" Him your actions will then follow and be righteous.
But why then does everyone not do the same righteous things, like pray the same way, eat the same foods, and make the same pilgrimages? Well, there are a few reasons I could give but they are all speculation on certain Christian's faith or the nature of God. That would be more of a philosophical discussion.
Everything that a Christian should do is summed up in a single verse. No Christian can neglect this verse, and, likewise, I have never heard of a denomination that would not agree with its first sentence:
31 So whether you eat or drink or whatever you do, do it all for the glory of God. 32 Do not cause anyone to stumble, whether Jews, Greeks or the church of God— 33 even as I try to please everyone in every way. For I am not seeking my own good but the good of many, so that they may be saved. 1 Cor 10 NIV
This should, and usually is, the prime thought of every Christian when they do something. They ask "Am I glorifying God right now?"
Christianity is about you coming to God as you are; after that, God, when you are willing, transforms your person into one capable of righteousness. It is not about your people coming to God, as in Judaism, and it is not about the world submitting to God, as in Islam.