See: https://en.wikipedia.org/wiki/Sad_Puppies
We can't have nice things.
I had been to several worldcons before sad puppies happened and that is literally what was being said about the nominees and winners.
Just compare to the lists of books from the 60's to 80's to the ones from 2000 onward. It's hard for me to say the quality is still.
I've read ~half the winners from 1960-1980, and a slightly larger proportion from 2000-2020. I found the more recent novels had more interesting concepts and vastly improved writing. The quality overall has increased significantly. Pretty painful to try to read eg Asimov nowadays
Sad puppies at least was completely honest about it. I don't agree with what they did, but it's honest. Everyone's pretending like they're voting for things nobody has read because they read them and not because the author has been "blessed" as appropriate for accolades. Also, not saying it should be a strict popularity contest.
Also, 2000's looks pretty normal and it doesn't seem to kick off until 2010+.
I could be convinced, though. It's hard to pick out a book from the last 15 years which which will be on the read list 30 years from now. Except The Three Body Problem, which I loved and I think will last.
So, I'll check back on this in 30 years and see how it's aged.
If I were asked to pick winners from the last 15 years that will still be recommended reads in 2050, I'd pick Ancillary Justice and The Fifth Season. From nominees not winners, perhaps Seveneves or Too Like The Lighting would qualify. The most recent book I can say will definitely be on the to-read list is 2000's winner, Vernor Vince's A Deepness In the Sky
I wouldn't go that far, Asimov is still awesome, with all the weaknesses that have always been in his works but with all the strengths, too.
That said, I agree that the SF/Fantasy scene has gotten some really amazing works lately. I don't agree with all the Hugo winners of the last few years, but that's because we have so much good competition lately :)
Some of the Chinese controversy about the Chengdu's WorldCon last year was as much about that natural sway in attending membership simply by being hosted in a controversial country like China no matter what else happened. It's called WorldCon for that reason and that sway in voting membership was always somewhat intentional to keep the Hugo Awards worldly and diverse. Some people were always going to have issues with a Chines WorldCon, even if they didn't also end up very publicly making mistakes.
Then in 2023 there was the self-censorship incident for the Chengdu Worldcon (and also some question about the ballot for selection of Chengdu in the first place, I believe).
Now this.
The Hugos are really having a lot of trouble recently.
That was as much a part of the controversy of the Chengdu WorldCon as any of the mistakes they made. The WorldCon was built to welcome that sort of diversity of opinion from an entirely under-represented part of the world in voting to that point. Even if the Chengdu WorldCon hadn't made silly mistakes it still would have angered a lot of people by how much it proved the Hugos actually aren't about "groupthink" and try to get a diversity of opinions.