I finished the story, quite liked it, thought it was great.
But THEN I join you where it just died and got so boring after. I had no problem "grinding" in D3, so what's different? They somehow managed to make the core of the core game not worth doing.
You could accomplish something in a 20 minute session of D3. You could get a rift done, maybe two, get enough stuff to upgrade something or find a better piece of equipment. You can’t get anything worthwhile done in D4 with only 20 minutes.
I did play d3 on the first few weeks when it came out and downed Diablo pre nerf. I remember not liking the grind but that was when only DH could effectively farm, I built a full tank barb with life steal and heals