Paul is absolutely important, but no more or less so than the other Apostles. They all spoke the Divine Word, he just happened to actually be able to write as well. He was a brilliant man, obviously, and a Saint, but he’s no more special than any other Apostle, IMO. Many of his “innovations”, such as his acceptance of Gentiles, were not unique to him, but had begun already, before he was even Christian. He was just very good at making a clear case for it.
What I find interesting is how downright obsessed many Jewish scholars of Christianity are with Paul, as if he created Christianity whole. There are countless books by Jewish authors about Paul and his role in Christianity, all seeming to overlook the fact that Paul had to work his butt off just to get accepted as a Christian at first. When you read his epistles, it’s obvious that he constantly labored under some suspiscion by other Christians, even when they accepted his teachings. They were only human, after all, and Paul wasn’t exactly the kind of guy they were expecting to join up with the Church. Everything he did and said seemed to stir up controversy and misunderstanding, and even Peter commented on that, saying that Paul’s writings were “difficult to understand”. I think it’s very telling that Peter had to include his “blessing” of Paul in his writings.
Of course none of this is intended to tear Paul down, as we’d have less than half of the New Testament without his efforts, and we are all enriched by being able to read the writings of an Apostle today, but we have to understand the context of his labors. His life as a Christian seems to have been a struggle, at least for a time, and that must be recognized and respected.