3.5 has a ton of splatbooks, sure, but they’re expansions. You go in one, if you want, at character creation to pull out a cool class you want to play. Not playing something out of that book? Then you never need to think about it. It’s not like you have to have encyclopedic knowledge of all the hundreds of splatbooks; all the rules are contained in the DMG and PHB, just like with 5e.