I get the feeling the game diluted itself over the years, specially after "Fall of Oriath" and I would've enjoyed it even more in a less bloated state. It's only natural that the company involved would slowly but surely switch from small-but-dense-in-quality towards "more shit = more money".
I mean, you're not wrong, but man was running the same four acts 3 different times worse than now. The real problem is the complexity of the mechanics they put out now. Used to be they added stuff like shrines and essences, fairly minor inclusions. Now they tend to add more complicated stuff, some of which really feels like it benefits from keeping a spreadsheet (betrayal).
Part of the problem though is that most builds invalidate most content by the endgame, so it rarely matters what enemies/bosses you are facing, because you are annihilating them before they have a chance to do much. So they kinda have to rely on these complicated addons to add variety.
I also think the problems with meta builds, build power differences and balancing thereof is essentially what Sawyer was trying to avoid when he made the other PoE. Massive build variety but impossible balancing vs good balance but no build differentiation, which is better and why? (the former, obv but it's still flawed)