D3 is in a weird place in that the more you play, the higher you progress, the more actual skill is needed, and awareness of certain enemy types, etc. Pushing high greater rift progression is like playing a completely different game than just leveling a character to 70, or even lower greater rift/torment progression. Obviously, it's unfortunate that so much of the ability to push higher greater rifts is tied to what set you're wearing, but that's the game. It's very set oriented. Hell, the "non set" Legacy of Nightmares builds are even MORE restrictive than the set builds, because you need ancient versions of everything, specific rolls, etc.
I really like some things that Path of Exile and especially Grim Dawn do. Where they lose me is asking me to play the same campaign content over multiple different difficulties before I get to endgame shit like maps in PoE. That is the dumbest fucking game design, man.