To preface this. I've just finished my first co-op run through of D:OS1 with a friend and it was an absolute blast, probably the most fun I've had in a game in a long long time, though it took a very extended amount of time to finish due to our schedule differences.
I'm rather late to D:OS2 and have only just started my own playthrough in the last month, and while I've been enjoying the improved characters, writing, and more concise dialogue, the gameplay itself has been truly suffering.
In D:OS1, my friend and I went wizard plus ranger while rotating out companions based on our needs, and battles were always dynamic and interesting with all the abilities and spells we had. We could stage an ambush and make enemies run through a gauntlet of fire, we could set up an ice field to give them the slip, we could make it rain and taze all of them, we could even set up an ice prison, teleport enemies inside, and charm them to make them cagefight each other. It was absolutely hilarious with all the combat options we had, and it made battles equally interesting and challenging when the AI turned the tables on us by using those spells forcing us to think on our feet to adapt to the new unpredictable situations where half our party is unexpectedly incapacitated or even hostile towards us.
D:OS2 on the other hand has been completely sterile. With the addition of magic and physical armor that prevent any and all statuses, the combat in the first half of any battle has been completely reduced to a 1980's style hack and slash arcade game. And afterwards? Sure there's lots of statuses you could apply after their armor is gone, but why would you want to use the vast majority of them when you can stun them permanently? The last half of every battle is just beating dead horses that can't fight back. All the interesting mechanics and options have been completely neutered. Sure, I could attempt to play the game the way I did D:OS1, but then that leads to substantially more difficult fights with the increased difficulty in D:OS2, because the AI abuses the new system like no tomorrow. The way combat works now, it forces you to play a very specific style, regardless of how tedious or uninteresting it is, or you'll be heavily handicapping yourself. The entirety of combat in the game has been reduced to hack and slash their armor, stun, hack and slash until they die, and if you dare stray from the formula, you're punished for it.
I can't for the life of me understand how a sequel from the exact same developer released mere years after the original could have fallen so far from their previous masterpiece. D:OS1 is one of the only RPGs to truly implement a combat system where battlefield conditions could be manipulated and become an integral part of combat, yet D:OS2 throws all those mechanics out the window and makes them useless.
Let me take a step back for a moment to give a background on my perspective. I've actually played the aforementioned 1980's hack and slash arcade games, and am admittedly old enough that those were the flagship games at the time I played them. I've since dabbled in every genre and especially enjoyed RPGs, from Baldur's Gate, Fallout, Diablo, NWN, TES, if there's an RPG of any prominence, I've probably played it, and I've completely enjoyed all of them. Also as a completionist, I tend to progress slowly as I stop to read most things I find and absorb as much of the game world as possible. And that brings me back to my current situation, 30 hours in, struggling to force myself to go any further, and having to make a hard decision. For the first time in my life, I'm going to use Cheat Engine in an RPG. That's how utterly abysmal the combat system is. It's so mindless and uninteresting, I just want to completely blow through it and bypass it altogether, because as much as I love the story and characters, I absolutely loathe the combat system. Is the combat more in depth than a 1980's hack and slash? Obviously. But to regress this far and this hard after D:OS1, it's shocking. I have never been so disappointed in an RPG in my entire life and it's truly saddening.