Good music is subjective. Aside from the guitar skills involved in shredding, I think heavy metal is probably the worst genre of music.
I don't particularly like Mozart but I'd be an idiot to say it's not good music. On the other hand most people agree Taylor Swift does not make good music, having released lots of samey 4 chord songs with incredibly simple melodies, but she's one of the most listened artists of all time.
The complexity of the music or the technical skill of the artist has nothing to do with it being good or bad. Music anywhere on the spectrum from simple ambient noise to symphonic formalism to simple and infectious can be good or bad based on the taste of the listener.