Maybe because they mostly wasted their talent on dull, basic songs and belted the hell out of every syllabe to make an illusion of emotional depth?
Or maybe because even when they got to sing good material from time to time, they always ruined the songs by trying to awe the publicum - sadly they couldnt find other ways to do it than senseless screlting what sucks the soul out of every song...? Just guessing

Lies.
Mariah songs are NOT basic, at all.
The belts are what makes them different 'cause not everybody can do it. They are special.

You don't think songs like Hero and One Sweet Day are basic?
I mean she has good ballads, but she has basic ones too.

I woke up like dihhh I woke up like diiihhhh

EDM trends

Almost everything in the 00's was pretty terrible imo except for a few moments here and there.

The post grunge rock trend, the punk trend, EDM/Dance craze, Urban/R&B (though I liked some of it when it first started becoming a trend), etc were terrible.