Some thoughts on Diablo 4 (D4) as per your question. In terms of ARPGs, I came from Diablo 3 and, way back in the day, Dungeon Runners.
From my feelings as a player, as well as reading from the community, the primary criticisms from D4's launch have been the way it handles items and endgame content. At original release, I know a lot of people who tapped out around level 75-80, with level 100 being max.
I am personally quite pleased with how the latest season addressed these issues. With the elimination of yellow (rare) gear as candidates, good drops feel a bit rarer (more time spent playing; less time scanning items). Reviewing loot can still feel a bit tedious at certain points in the game, but you eventually reach a point where a legendary item needs to drop with an asterisk before you look at it, again allowing you to focus on playing over sorting.
You said in a comment that you are in it for the progression. I find character development rewarding but skewed; the early game is fast paced and incentivizes rushing to get to the final difficulty level, when progression peters off and becomes rather marginal. In Diablo 3, you wanted to play higher difficulty levels to have better drop rates. In Diablo 4, it's not so much the drop rates as the quality. Items from the highest tier completely outclass items from even the second-highest tier, meaning you have to keep starting over from scratch as you move up. I'd rather it be balanced in terms of drop rates, thus still having a small probability of carrying a midgame item all the way to endgame.
Some endgame activities are more enjoyable than others, but they have different rewards that encourage you to have some gameplay variety. Boss farming is probably the most tedious endgame activity. It is done to get the most valuable and rarest pieces, the uber uniques, but requires you to also grind bosses that realistically won't help your character other than to get materials to summon the higher chance bosses.
My friend who plays PoE and has tried D4 is well described by @Neuromancer49's post; the lack of complexity turns him off. If you're okay with trying something simpler and are at all interested in the campaign/story, I think it's worth getting. I know there's a vocal group that prefers Grim Dawn and the Diablo 2 die-hards seem to dislike D4, for what it's worth.
Lastly, the art and sound design team did a spectacular job if you like Diablo's aesthetic.
Glad you found it helpful!
Ah, the labs sound similar to a type of dungeons that were part of last season's theme. I liked them too. There's a new pit mode that is similar to greater rifts in Diablo 3 if you remember them. Not quite running through traps, but running through procedurally generated dungeons to reach and defeat a boss as quickly as possible. Those bosses started out with some cheap one-shot kills (now nerfed), but I find them pretty fun and prefer this mode of dungeon + boss to the regular boss rushing.
As Grim Dawn has been on my list, do you mind sharing why you couldn't get into it? Anything I should know going in?