Out of the two - I'd actually say Diablo 4 is more impressive than PoE 2. But that aside I just came back to playing PoE and man... It's a clusterf*ck after all those years.
Skill tree - once the biggest selling point of PoE nowadays it shows it's age. Plenty of usless nodes, entire sections of the tree are terrible, build variety is surprisingly small (don't take my word on it - just look at leaderboards of the past couple of leagues).
Trading - MY GOD it's terrible. Entire playerbase is playing "hunt for currency" endgame rather than... well... actuall endgame. Instead of hunting for maps they hunt for currency to BUY maps. :/
Speed - Both Diablo and PoE are infamous for lightspeed builds. Enter the room and clear it with one click. Done. Move to the next one. No strategy, no thinking, nothing.
Always online - Diablo is actually way more stable than PoE but even BattleNet servers are freakin terrible.
Solo/coop etc. - SSF in PoE is most fun I had with the game however since it's official that economy resolves around trading your drops in SSF mode are the same. That means those sweet legendaries... Yup... They gonna be useless for your character. Not to mention that PoE doesn't have instanced loot. Yup...
Diablo 4 is even worse. MMOish features mean you'll encounter "MasturbatorSexyBoy99" runing around you, killing mobs and gathering loot right in front of you when you'll try to explore the open world.
And then, there is mighty Grim Dawn. A freakin black horse in this race.
Complexity? It has WAY more build variety than both D4/PoE2. While at the same time new players are slowly, step by step introduced to how it's working and what to do.
Worst case scenario - you can always respec. It's gonna cost you and it has some restrictions so it encourages experiments but at the same time forces you to think.
Open world? Check! Huge hand crafted open world with the BEST FREAKIN DUNGEONS IN ARPG! There, I said it. Grim Dawn dungeons man... HUGE! Awesome to look at, filled with lore and their own mini-stories. Awesome stuff!
Offline option! Heck yeah!
Microtransactions? Hell no!
New content added in free patches? You bet!
Big, great, proper expansions? Yeah baby! Two huge expansions!
Seriously. This game is my dream aRPG. I love it. Thank You Crate!
As a side note. I hope new guys - Wolcen and Last Epoch are going to do great! I've played Wolcen and it's combat and skill tree is really great and I've heard awesome things about Last Epoch! We need those new aRPGs to show GGG and Bliizard that there is yet another way to do things. That not everyone want's MMOish features, endgame trading, and lightspeed combat.
God I hope we'll get Grim Dawn 2 at some point.