Take the concept of transubstantiation. While it is part of Roman Catholic doctrine, a discussion I had with two priests demonstrated to me that not even two priests shared the same understanding of transubstantiation. One believed it as a literal thing; the other a symbolic thing. I know there are priests that are heretics. Although I don't know if you understood them correctly in this case. The bread and wine actually become the Body and Blood of Jesus Christ (that could be described as "literal") -- but it's not a molecular change (which could be described as "symbolic"). It's defined in very specific terminology and when descriptive terms are thrown around they could cause confusion for someone who doesn't already understand what's being expressed.
Doesn't change the fact that millions of people believe exactly the same doctrine as defined by the Catholic Church (same for other churches), whatever your cirle of friend or acquaintances believes.
"I know there are priests that are heretics. Although I don't know if you understood them correctly in this case. "
Actually, I understood them just fine in this case. They differed in their understanding of transubstantiation. I know what the doctrine is, and I know that there is not universal acceptance of the precise definition, even among RCC priests.
It was an interesting discussion, that one. It went on for about three hours, over some very fine old Port. I enjoyed it enormously, as I have enjoyed many discussions about doctrine in several denominations.
We left it undecided, I have to admit, but all three of us had quite a rosy glow about us when we parted.