i agree, learning to hear differences and assessing sonic qualities is a learned skill, moreso for some than others, but true for all
for some top tier dacs, their sounds can be very very similar -- couple examples in my travels...
i had the bricasti m1 mdx, and the weiss 501 side by side for a month, a-b-ing back and forth, each using their own streaming front ends, both very highly respected and prized dacs... as much as i tried and tried, i simply could not reliably tell the difference ... so in the end i kept one and sold the other based on non-sonic considerations
otoh... i compared a topping d90 mqa to a chord qutest... listening to a single song, i could tell the chord was significantly better... clearer, more musical, more extended, less mechanical in presentation