What you mention with Diablo, it's almost a carbon copy of what happened with Starcraft. We went from a frankly dark universe in Starcraft 1 and Broodwars, with an actually evil character in Kerrigan, to the Starcraft equivalent of a Marvel Movie (Including whitewashing Kerrigan's character through retcons to such an extent it's not even funny). It's pretty clear that sometime after releasing WoW, Blizzard lost both its balls and its talent.
SC2 really is not good. Even when it came out I didn't like it, but I recently replayed it, and holy shit it aged horribly and is truly just bad all around. It starts below average with the first installment, and gets much worse as it goes. Blizzard is a classic example of studios being skinsuits that rely on reputations built by white men who left the companies years, or even decades, before.
I tuned out of Starcraft 2 after Wings of Liberty and only know the cliff notes about Kerrigan becoming a retarded star god or something. It irked me enough that Blizzard wanted to rip you off by selling you the same game 3 times at full price, but doing a 180 on Brood War Raynor was too much:
Jim Raynor: Fenix! No!
Kerrigan: What are you worried about, Jim? He died the way all Protoss hope to: in combat.
Jim Raynor: He died because you betrayed him. How many more noble souls do you need to consume before you're satisfied? How many more innocent people have to die before you realize what you've become?
Kerrigan: You don't even know what you're talking about, Jim!
Jim Raynor: Don't I? I'll see you dead for this, Kerrigan! For Fenix, and all the others who got caught between you and your mad quest for power!
Kerrigan: Tough talk, Jimmy, but I don't think you have what it takes to be a killer.
Jim Raynor: It may not be tomorow, darlin', it may not even happen with an army at my back. But rest assured; I'm the man who's gonna kill you one day. I'll be seeing you.
Well Kerrigan was right and Fenix can go hang, I guess. F
The way Diablo IV treats its story is something that put me off Monster Hunter: Wilds's story, but that version is fucking mild compared to Blizzard slapping you over the head repeatedly with this shit.
Even better, Raynor murders his supposed old best friend to protect Kerrigan, who he swore to kill as punishment for all the evil she had committed, because vagina is perfect UwU. Not only does he not avenge Fenix, but he kills another friend to protect the woman who killed Fenix. You did yourself a favor. Not only is the story and lore obliterated, but the gameplay gets progressively worse as well.
Speaking of story, in the Heart of the Swarm, it
really goes out of its way to try to pretend that Kerrigan doesn't remember being evil and it wasn't really her who did it, but then still has multiple missions of her slaughtering scores of innocent people for her revenge. But it will show her not slaughtering
each and every single one of them, sometimes, which is supposed to redeem her... somehow? As if murdering 99 innocent people is fine but 100 innocent people is just too much. She lets a few ragtag survivors leave Char when she kills Warfield, a good man who was protecting innocents as much as he could. She allows
some evacuations before attacking Mengsk's capital to slaughter everyone who gets in the way. However, she
does slaughter every single Protoss colonist on that ice planet that were just minding their own business, and is totally fine with it. That's not even getting into the level where you infest tens of thousands of humans to use them as disposable shock troops against Dominion forces. Yet, consistently, the story wants us to pretend she is a righteous hero.
Oh, and it gets even worse when they bring back Fenix as a robot in the Protoss installment... Such shitty, nostalgia bait garbage that shows they had zero faith in their game by that point. I never touched the Nova cash grab DLC they shit out, but it looked like it was somehow even worse than everything that preceded it.