How does one defiine good/bad taste in art, if at all?

[Bridge]

But technically you could consider anything to be art.

Therefore I propose that art must be something that can be evaluated using objective criteria in order to not just be anything.

This is easier with traditional classical music, where harmony creates rules for how to make pieces sound not like crap and compositions can also be analyzed structurally to determine their depth.

I completely disagree. Those "rules" do not mean anything. Ultimately, if something sounds good and it does not follow traditional "rules" regarding harmony, then it is good. The idea that classical music is objectively better because it has a bunch of rules is exactly why nobody respects it. It is a moronic assertion. Structure likewise does not mean anything. I truly pity people that listen to a composition and actively try to identify the structure and compare that to the rules they've been convinced are necessary. I mean, if I listen to a piece in sonata form then I generally know how it's going to go, and may passively think "now the development begins" or something but it just doesn't matter. It's only useful when you're analyzing pieces in order to learn from them.

Case in point: The blues is theoretically in complete violation of traditional harmony and diatonicism, what with unresolved dominant chords and blue notes. But it just sounds so good. Likewise, jazz doesn't conform to the rules of traditional harmony - it has spawned its own rules that misguided students memorize as per their teacher's orders.