What is the consensus on the audible sound quality comparing a brand new or refurbished 1985 $200 CD player when compared with modern digital gear? (Same disc via a high quality transport and modern DAC)
Some VERY early CD players (1985 would count) had improperly designed filters which could cause foldover, and/or the effective bit depth might not have been good (noise). This is where the reputation for digital sounding a certain (bad, metallic, harsh) way came from, supposedly.
Modern cheap DACs put expensive 1985 DACs to absolute shame, I think that's uncontroversial.
If you feel that there is an audible difference between the 1985 CD player and modern digital gear, when did all quality digital become "a solved problem" and essentially have no sound quality of its own?
~$120 "prosumer" DACs were transparent for normal listening about 15-20 years ago, and in the past 5-10 years have reached "audibly transparent even in really extreme scenarios, with really high gain".
A high-end DAC or CD player was probably just as transparent by the early 90s.
Digital recording has been superior to analog recording in the studio for (depending on who you ask and what their priorities are) for 15-30 years. Today there is no reason to use tape unless you are after a certain type of distortion, which is valid, but impractical.
As for digital audio formats - good quality (320kbps) MP3 was indistinguishable from CD for most people for most recordings about 15 years ago. Streaming quality is close to this or superior in many cases.
As for "sound quality of its own" - this is an interesting question. For a long time, the only discernible difference between the actual DAC section of a given piece of gear would be in the noise floor or jitter noise if it was somehow extremely bad. The FR should be flat. Whether the analog amplification after the DAC itself is also flat and low-distortion is another question. I generally don't think of noise as having character or "a sound", so if you agree with that, DACs have all sounded essentially the same for decades.
This is really part of the nature of a DAC. It turns a series of numbers into a continuous signal. It doesn't have resonances or anything, and the filters used are not very exciting or complex, and mostly operate outside of the audible band, again by nature. So a DAC should not be expected to have much of "a sound" in the first place.
It is like saying a DVD player might have "a look of its own". Like what, exactly? A bit too red? "Gritty"? How would a DVD player even do that? It's not how the format works. DACs are just like this. There may be some analog shenanigans happening after the DAC to create character, but not within it.