I'd say taste-as-subjective-something is largely irrelevant. If something "looks good" but hurts to use, that's not much help. If it looks like ass, but is a delight to use, that's not good either (because most people won't reach the point of actually experiencing it). So you need "looks good" and you need "actually delightful to use". Taste seems to be orthogonal to both of those. Or perhaps (two kinds of?) taste is involved in each one.

At which point we define taste as two unrelated things: skill in aesthetics, and skill in ux.

I've seen apps that looked amazing (Taste #1, aesthetics) but made me go, "Okay, did they actually try using this thing?" (Taste #2, usability). I think these tastes are completely orthogonal, from personal experience. I think the vast majority of designers suffer from Total Usability Taste Blindness.

(And, though it feels a bit mean to point out, the vast majority of FOSS suffers from a total absence of both. The winning projects only win because they have no competition, they're the only free option available.)