They all generally affirm the same things though, it’s just the Bible doesn’t say exactly how to practice Christianity, so add two thousand years and weird theological technicalities like real presence (and how much real is the presence, it’s a spectrum), church structure and organisation, authority, etc, then you have a bunch of different denominations. Most of them though do actually respect each other in an ecumenical fashion. The “Catholics aren’t Christian” sect would be a fringe minority, the same type who would believe the world is 8,000 years old and that the KJV is the only proper English translation.