In the end you also need to accept that reaching something totally transparent throughout the (re)production chain is going to be impossible.
I debate with myself whether I am lucky or cursed.
Perhaps I had enjoyed poorly performing LP and FM radio systems so much over the decades before digital appeared that the improvement of digital sounded like perfection to me, but I for one found that whilst I easily hear differences between microphones and the various tape recorders I used the very first time I used digital I couldn't hear any of the usual differences between the recording and the microphone feed, they sounded exactly the same.
Maybe I was listening for the normal big differences and missed tiny subtelties but I was very pleased by the results from day 1.
Almost 10 years ago I carefully compared several DACs on music I was familiar with and heard no difference, though perhaps I could have persuaded myself one had a minute increase in detail but I couldn't be sure, and it certainly wasn't enough to bother about.
I do hear differences in some reconstruction filters on DACs where they have been selectable, but by no means all.
I hear clear differences between my 4 record players, so my ears are not completely made of cloth, but even they have been tuned by ear and I like all of them.
I know no simple number can define what sounds nice since some distortion is barely noticeable, some is nice (tape saturation is a nice way of limitimg ime) some sounds dire at low levels but since I listen on loudspeakers it seems to me that my source would have to be pretty awful not to be masked by speaker imperfections.
So overall I think I consider myself lucky, I think, I can enjoy my records without worrying. As a hobby dicking about with hifi has come to an end for me since I pretty well never listen to music and am concerned by some aspect missing or wrong with the sound quality, mind you I have loudspeakers I really, really like.
I do find background noise between tracks irritating on FM tadio and LPs but I have only ever heard it on CD when the recording is an analogue original and the tape noise is still there.