Wolf, I don't know that it's so much generation thing -- it could be, I'm an old guy, too -- but it's undoubtedly in large part a personality thing. And if I misphrase what I'm saying easily misunderstood to be me saying it's an intelligence thing, which it is not. Well, maybe in a couple of cases I can think of it was, but I'm talking about a broader scope than those couple of guys.
I work with a guy who plays Rifts, and the reason he me that he and his brothers went with that system way back when was that D&D wasn't complicated enough for them. That was first and/or second edition from the way he tells it. From what I've seen of Rifts, it's too complicated for me. Not that I can't understand it, but the fun/work ration is too small. With Pathfinder, there's potentially a lot of work to do in deciding how you plan to develop your character and what you're going to have to give up in one area to gain in another and on and on ... but in that system, unlike Rifts, that's actually part of the fun, for me.
Also, I would agree with you that for all that the new D&D brags about being modular, Pathfinder is already modular enough that it's not hard to look at what you don't like and say "Naw, I'm not using that part". (Note that is not a swipe at 5e, they specified a plan to be modular and succeeded quite well, it's also a very well designed game. Just saying it's over reach if anyone tries to claim they were first.)