Yes, Paul could be called the founder of the Roman Catholic church, though I'd add caveats like the churches already existed and maybe Constantine is and maybe that one pope that demanded supremacy over the eastern churches and didn't get it is. It seems like there was some bitterness between some churches over Paul being seen as usurping Peter's place.

And there was this long procession of church fathers writing important texts and being saints for a long time before being declared heretical long after their death. Marcion and Clement of Alexandria are examples. This is why I say that modern Christianity is the result of repeated purity tests. If you read Origen, there's just no reason to call it heretical, unless the purpose is a political purity test designed to create enemies. Its statism. Same with Arius, and you cab still observe the silly attacks on Arianism made by Orthodox, who seem to need to maintain the attack for centuries, but if you read what he actually said, there's no problem and there was no need to create the Nicean Creed, and even Constantine wrote to the bishops that they were being ridiculous.

But what followed was mass murder... And over time, the hundreds of different churches and ways of understanding Jesus Christ were replaced with one church - the Pauline church. And Paul was either a statist or knowingly courted state sponsorship, and I think it contrasts sharply with what Jesus said.