I just finished the last of the content Saturday (got to 100 seasonal and finished all the seasonal journey tasks to get hidden title). Here are my thoughts.
I was fine with the game up until about 70. Even then, I was still good until about 78-80ish. The problem becomes that for the last 30 levels, there is no greater tier of armor/weapons than Ancestral. So if you get a decent piece of gear, with the 4 affixes you want on it near 70, there's literally almost no chance of getting a better piece. Sure, a 800 piece might be slightly better armor value than a 725, but since your damage reduction from armor is lowering as you level, it's not really worth it if you have the proper affixes increasing your DR directly, and adding to the proper damage categories. Even pieces with 3 affixes are problematic when the increasing enchant costs get out of hand fast. I've dropped 35 million gold on a piece trying to get a decent last affix, and not gotten it... multiple times.
The game also needs something more to do than nightmare dungeons at those levels. Open world stuff is practically worthless after you get to a certain level, because the enemies lag behind you in level, which incurs the XP penalty, which they made worse with that patch not too long ago. You have Helltides, but even then, they're only 3 levels above you, which was fine when that granted maximum bonus, but now you need +10 to get max XP bonus.
I don't know if I'm up for the seasonal grind if they're literally going to be back to back like Season1 and Season2. I expected a month or so break between them... maybe do a prelude event on eternal or something for the month. Give me a reason to play my original Eternal character again. But at this speed, it just becomes a graveyard for your seasonal characters never to play again. Also, inventory is going to get worse and worse with stash as you have more seasonal characters moved over to Eternal at the end.
I definitely got my money's worth of play time, but kind of wish there was something to keep playing other than time-limited seasons, as they just seem to be FOMO content.