Most Protestants (who weren't Catholics before) who studied history remained Protestant. It would be one thing if the Papacy and the Vatican had a perfect interpretation of scripture and had stuck to it, but that's not the case. Instead the RCC ended up with their updated changing version of Christianity that in some cases eschewed scripture in favor of catechisms. Just as the Jews ended up favoring the Talmud they created. So the problem of Sola Scriptura for Catholicism is that it doesn't allow for the extrabiblical dictates the RCC came up with over the centuries. The RCC like most others decided to do it their way. Otherwise the RCC would be the same now as the early church up to the 4th century, but it clearly isn't. The RCC morphed into something different. The RCC seems to be currently morphing into accepting and promoting LGBTQQIP2SAA+ and transgenderism. Lots of Catholics and apparently the Pope is onboard with that. There's just too much wrong with the RCC and Catholicism past and present to make the claim of being the one and only true infallible church. Really the Eastern Orthodox Church is closer to that than the Roman Catholic Church.
Protestantism already accepted contraception long ago, with some accepting abortion and performing gay marriage more recently. The RCC, almost uniquely, opposes all of that while striving to accept all humans as we’re all sinners and there is no Catholic teaching
anywhere promoting LGBTQQIP2SAA+ and transgenderism.
Again, it matters not what many Catholics including even the pope are on board with-Catholic doctrine is the key, and that hasn’t changed. That’s what the gift of infallibility is all about. Some popes have personally believed in heretical views at times, but no teachings were changed.
If you wish to study historical teachings of Christianity you’ll need to immerse yourself objectively in the early fathers. There you’ll find an almost distinctly non-Protestant flavor to the basics: liturgy, church structure and hierarchy, baptismal regeneration, justification, the Eucharist, the real presence, the sacraments, Mary, the list goes on. The eastern and western ancient churches to this day happen to be virtually identical on these matters for all real and practical purposes even after centuries of isolation, due to the teachings/Tradition received at the beginning, while there is no consistent universal Protestant position on any of it, being all over the board on some while rejecting others outright. This is because Protestantism is mostly based on individual interpretation of the Bible, alone, centuries after the revelation, itself, took place.