Diablo fans HATED it. But game journos loved it.
I was a big fan of Diablo, I was a bigger fan of Diablo 2, in fact I was an early tester of Diablo 2, Blizzard actually mailed me a disc with the game on it (the days before we could easily download games!), a year before it came out. And I LOVE Diablo 3, and think it's an improvement over the others. And I know others who feel the same. So it's not universal that Diablo fans hate Diablo 3. It's mostly just that the ones who do hate it are really, really loud about it.
As for the topic at hand, I still think that professional news outlets have no business reviewing or putting a score on an UNFINISHED game. Only independent YouTubers and such should really be doing Early Access reviews, in my opinion.
Diablo 3 has changed significantly too and it has become a lot better, I don't think that people actually genuinely hated it just that it was a disappointment after waiting such a long time that it was so different to Diablo 2 and then there was also the connectivity issues on launch.
I remember it, it was almost impossible to even play the game at launch.
I grew up playing games like Diablo 1 and 2, and this is obviously based on my own personal experience but the overall sentiment isn't that Diablo 3 is awful and that they hate it but just that it was disappointing.
I think that there's a lot of emotional investment in Diablo 3 too that caused a more negative reaction on launch with all of the issues and very different style, but a lot of that dies down and I really think that most of the negativity was due to the connectivity issue and the auction house.
I watch a lot of speedrunners for Diablo 2 too who stream and have played it since day 1 non-stop and they say the same thing, they don't think that Diablo 3 is a bad game just not what they wanted it to be.
A lot of people tho think that just because a game isn't what they want makes the game bad.
When it comes to Baldur's Gate 3 the response hasn't been like that at all, and I also think that people shouldn't overestimate the fans of the first and second games too.
Something worth noting is that it's usually a minority of people who finish games, TLOU2 had a 58% completion rate which was abnormally huge.
Most don't get anywhere near that, only 32% for example finished DA:O and I consider it one of the best RPG's ever made.
Just because Baldur's Gate 1 and 2 sold well doesn't mean that there's millions of hardcore Baldur's Gate fans who are super ultra invested in Baldur's Gate 3 being accurate to a niche thing like DnD.
And then look at a game like Path of Exile, it's fundamentally different than Diablo 2 in so many ways but people still regard it as a spiritual successor to Diablo 2.
Edit: Fighting games again are actually a good example, because so many of them have fundamentally changed to the point that they're unrecognizable and yet have been well-received because of the casual audience.
But then meanwhile the hardcore playerbase just sit there in disappointment.
I don't think that Baldur's Gate 3 is that drastic, but it's definitely going to have part of the audience that are going to be disappointed.