This is an interesting charge. When and by whom are relevant questions. If the early Church was corrupted, what were the corruptions,
How was it off base from the start? Didn’t Jesus personally instruct the Apostles? Was His teaching somehow flawed?
There is a difference between people being people (vain, greedy, etc.) and beliefs. While the whole “I belong to Apollo” thing was vanity, the Truth of Jesus Christ wasn’t at issue.
So, going back to the original question, if the Church has been corrupted “since the beginning,” how do you know what to trust, and what not to trust? Since the Canon of Scripture was closed in 397 AD, what corruptions took place after that? Were they corrected? If so, by whom?
For those who dissent from the Catholic Church, it is an easy charge to make that it is “corrupted.” However, when one goes back to the beginning, and examines the teachings, one finds that aside from defeated heresies, “corruption” began with the Reformation, and the removal of books from the Bible. From there, any number of novel teachings and beliefs have followed.
The novelties continue, such as “gay” clergy, support for abortion, acceptance of divorce, and a number of other moral issues. Since there is no recognized authority among non-Catholics (excluding the Orthodox), any belief can be supported by one’s own interpretation of Scripture. That is also why there are so many non-Catholic denominations.