That's your personal opinion so it's subjective.
Here's some bl I think are pretty, art style-wise
https://www.mangago.me/read-manga/kouguu_no_omega/
https://www.mangago.me/read-manga/kimi_no_yoru_ni_fureru/
https://www.mangago.me/read-manga/extra_oneshot_kimi_to_aruku_yoru_not_official/
https://www.mangago.me/read-manga/bidou_wakadanna_koi_shitau_wa_koushoku_otoko/
https://www.mangago.me/read-manga/even_dogs_fall_in_love/
https://www.mangago.me/read-manga/yuusha_yo_boku_ni_kashiduite_kobirugaii/
https://www.mangago.me/read-manga/tasogare_outfocus/
https://www.mangago.me/read-manga/snow_fairy/
https://www.mangago.me/read-manga/are_you_the_hero_s_boyfriend/
It's a genre and not a specific art style that artists are limited to. There's a plethora of all kinds of artists out there drawing bl. You'll probably find someone who's art you like. And it's okay if you don't too
It's the build.
The characters are built like two cardboard boxes, or refrigerator, or.....idk. it feels stiff.
And the hair isn't detailed.
And the eyes aren't as pretty.
Though, the vampire one, doyun(?) The uke basically, got THIS great glow up and the whole art in general. Ugh. It got so pretty.

Or yaoi art is like- REALLY really mid?