Yep. 90% of it is pure garbage technically, and I'm saying technically cause that is what rap is about, being technically skilled is something everyone will value, flow, lyrics, delivery of your vocals all fall into that. Whilst mainstream is just party music with no flow switches, no point in the lyrics, same boring ass delivery, a catchy but still very fucking generic trap beat with the same 808 and the same hi hats just different compression and distortion.
Underground does it way better, even if you look at the beats, it's still trap but it's much more creative, I mean look at $uicideBoy$, yeah you might not like them as rappers cause they're edgy and cause of the name but $crim (aka Budd Dwyer when he produces, 1/2 of $uicideBoy$) has legit the most godlike beats, it's still trap but he is much more versatile with everything and it all sounds different despite them as a group having put out like 240 songs since 2014. Another producer is thraxx, The Virus & Antidote, greaf etc