quality is definitely noticeable without bringing opinions into this. not always as much, and i'm not saying people can't like "lower quality" singers for example.
a lot of things are based on opinions, does it have a catchy tune? Do i like the singers voice? (not to be confused with: is he/she a good singer, 2 absolutely different things)
let's say 1 guitarist knows how to play 1 chord. and another one knows how to play 2.
objectively the one that can play 2 is a better (higher quality) guitar player. Does that mean you like the songs of #2 better? no, but that doesn't mean #2 isn't better.
to say that everything about quality in music is subjective is just wrong.