The complete answer concerning creeds, church identity, and worship
Claim examined: Church identity and unity
Scriptural Answer
Faith, Until you can provide PROOF from the New Testament that the body of Christ which is the church is "invisible", then you really do NOT know what you are talking about. The church of Christ is NOT some "invisible" institution that Jesus made when He said, "I will build my church" in Matthew 16:18. To claim that there are Christians in different denominations that teach CONFLICTING doctrines is NOT what the New Testament teaches. Your claim that churches follow apostolic teachings is NOT the truth. If they did follow the apostles teachings they would NOT be teaching that one is saved by "faith only" nor would anyone follow the teachings of "calvin" or of any other man but would rely on the word of God as their ONLY rule of faith and practice. Many denominations have their own "creed books" that are of men and NOT of God. To claim that one can worship God in any manner that he pleases is NOT what the NT teaches. God MUST be worshipped in "spirit and truth". (John 4:23-24) and to claim that one can worship God in any denomination that allows musical instruments is NOT worshipping God in "spirit and truth". "Let us hear the conclusion of the whole matter: Fear God and keep His commandments, For this is man's all. For God will bring every work into judgment, Including every secret thing, Whether good or evil." (Ecclesiastes 12:13-14). Those who have NOT obeyed the gospel, including you Faith, are outside of Christ and His church and separated from God. This INCLUDES everyone who is not a member of the church of Christ for they would rather believe what man tells them to do in order to be saved instead of what God has PLAINLY revealed in His word.
KJV Scriptures Used
Read each passage in its chapter and compare the Scriptures together.