the hate basically comes down to Destiny 2 ignoring everything D1 eventually got right in favor of trying to attract an audience of gamers who never stick around after the campaign ends.
Destiny's always been hated and there's no rational or logical reason for it, It just always was. People romanticize D1, but from the day D1 out, youtube was littered with comments how the game was dead, trash, etc. Now there's this revisionist history that D1 was widely loved, no it wasn't! D1 was hated from the day it released! The so called golden era of crucible for example, was really just a bunch of people bitching about how blink shotty was OP. I was there...
This is similar to Crysis. I was there in 2007, Crysis was widely considered buggy shit. Now there's revisionist history for some years that it's great. It was never considered great in 2007, I remember defending it in 2007 from hordes of people on forums telling me how shitty Crysis was, and not one person agreeing. It's also similar to Lebron, people hate Lebron, and they will rationalize it a million ways, all of which are lies. No, they just hate him is the facts.
That rant aside, I do find it funny that warmind's relative popularity proves to me that "fixing" D2 means mostly adding grind. So simple. I've stuck with it longer than most expansions for the simple reason, it's taking me longer to hit the level cap! And there's some pretty grindy exotic quests, EP which is fairly grindy, and crucible ranks are another long grindy thing. And that's it! Destiny halfway fixed. I will say Bungie is a little slow on that one. Just add some stupid counter that goes up, probably takes 5 minutes to code, and we'll all be addicted much longer LOL.
The main things that kept me in D1 for example in the long years 2 and 3, were grimoire score, and record books. Both removed from D2, both EXTREMELY grindy.
I literally sat there like an idiot and ground out 100 rumble wins for the grimoire,, at a winning rate of (probably) something like 1 in ten. Hundreds of hours probably for that one alone.