Seems to be a certain discrepancy; the Early Church had a mission to make sure that only the true teachings of the Church were taught, and went out to correct people who taught false doctrines. Now, there's so many doctrines flying around from different branches of the Church that even fundamental issues like the Trinity and original sin aren't always taught!
What happened? Why was there a fundamental truth when the Church began, but no truth now?
And blaming the Catholics or the Protestants or any branch of the Church doesn't answer the question; you may say that "We changed teachings because the Catholics were wrong", but that doesn't answer why the Protestants are so badly divided. Luther & Calvin knew the importance of maintaining true teachings, as they both had mini-inquisitions, persecuting people who strayed from their teachings (and in Calvin's case, actually killing a few); while I'm not defending Inquisition-style persecution, why has the mentality of "We need to maintain 1 set of teachings" gone away from so many Christians?
"For the time will come when people will not put up with sound doctrine. Instead, to suit their own desires, they will gather around them a great number of teachers to say what their itching ears want to hear." --2 Timothy 4:3