It's always a bit of a dice roll.
I'm not aware of any formal study of the issue.
As you noticed, the Internet is loaded with anecdotes. No doubt, many people will be driven by them even though they have minimal statistical relevance.
Yes...Asus is getting bad-mouthed more than it did 10 or 15 years ago. I've read why, but can't recall.
I think Asrock may have improved its ranking among the anecdotes in recent years. May not be valid at all, that's just an impression I get. Same with MSI. Maybe that's just because Asus has fallen. It's not like there are 25 brands to choose from as you might find in automobiles.
More than anything....you need to buy the features you at least you think you need and cross your fingers. Maybe give some attention to warranty and return privileges with your vendor.
Customer service is behind a lot of the disappointments you may read about....I would NOT expect to have a happy experience with any brand name in that regard.
The only brand I've had NO issues with is Gigabyte....signifying nothing at all. I'm just another anecdote.
Reddit would rank quite low on the objectivity scale, I'd think. But I don't know where you'd find anywhere that ranks high.
It seems that Asus is the most common "on sale" brand I see in my daily New Egg email alerts. That might mean that there is noticeable resistance to their suggested retail prices, possibly due to the negative comments you have seen.