Isn't it really about quality of recording?

Certainly there is wide variation in recording quality, but IME system quality has great impact on all recording qualities. A great/good system can't make poor quality recordings sound good, but it can make a much larger variety of recordings sound better than with lesser system.

I have over 2500 cd rips, these are recordings I've owned in some cases, well over thirty years. Point is I've heard these recordings over many years with different systems, some portion of these recordings I thought unlistenable with prior systems. With streaming system improvements I've made over recent years, many of these recordings I thought dead  have been brought back to life. For instance, just the other night I listened to Deep Purple's, Shades, 1968-1998 4 cd box set from 1999 for first time in a long time. I long considered these recordings pretty unlistenable, small sound stage, extreme panning, pretty poor timbre, compressed dynamics. Well I chose 1st cd, so early 1968-69 stuff, what  a revelation over prior listens, the added resolutions/transparency of present system vs. priors made this rather mediocre recording come alive in listening room. Sure the inherent limitations of recording remained, but I was now fully engaged where this couldn't happen prior. And this exact thing has been replicated many times over past few years, new life to formerly thought dead recordings.

Bottom line for me is as system improves so should estimations of recording quality. A good/great system should be able to engage you with a wider variety of recording quality than lesser systems.

I often hear talk about bad recordings and good recordings, but what are the particular qualities that qualify a recording as bad or good for you?

The only recordings I qualify as truly bad are those with totally quashed dynamics, generally victims of loudness wars. These are mostly 'commercial' recordings, genres I generally stay away from, most from digital studio recording era. Far fewer of these from analog studio recording era. These recordings are the true turds, no audio system can make them sound better.

The other problematic areas can be timbre and/or equalization anomalies. Timbre issues very closely allied to excessive compression, IME, allowing more micro dynamic expression makes up for some of these deficiencies. Freq. anomalies I generally  hear as boosted highs, less often, excessive or bloated bass.

Sound staging and imaging issues can be another area of concern.

With the exception of the totally quashed dynamics recordings, I've found vast majority of other challenged recordings to sound more engaging as my system has improved. Mostly its just sheer resolving and transparency that makes so many recordings more involving regardless of recording deficiencies. I've also found state of mind is important to maximizing listening pleasure with lesser recordings. One has to be ever mindful of individual recording qualities, quit judging the system with the mediocre quality recordings. I find interspersing known good quality recordings with the not so good brings things back into perspective, I'm then reminded my system is indeed capable of totally natural, highly resolving playback. Repeat this over the years and one falls into music loving mode far more easily. Listening in analytical mode all the time ensures dissatisfaction with far more recordings.

I built both mercilessly revealing and golden glow systems in years past. Golden systems could play only certain recordings, mercilessly revealing system certain others. Choices of recordings played was often imperceptible, it would only be in the long term I'd notice the limited choices made. After having experienced both extremes long term, defects of both eventually become intolerable, at this point I sought  another path.

The problem is not that revealing is inherently merciless, rather revealing CAN be merciless if sound qualities such as timbre and/or harmonic development is lacking or unnatural. I do continue to seek maximum resolution/transparency, but the timbre, harmonic development  capabilities must be top notch as well. I'd evaluate my favorite flavor as being just the tiniest bit warm of neutral, can hear full potential of great recordings, allows vast majority of mediocre recordings to be enjoyable, even low end of mediocre very tolerable, poor should rightly remain in intolerable category.

In my case, SET amps, DHT preamp, high efficiency horn loudspeakers have been the magic elixir. I won't argue subjective pathways others take, all good in my book.

Another aspect of tubes I don't think has been brought up in this thread, is tube equipment usage in recording studios. Some of my favorite sound recordings are from the era of tube recording equipment. This was era of essentially live in studio recording, not all this multi track, recording individual players at separate times and patching together. Some of the old studios were wonderful sounding venues and the natural resonance and harmonic development of tube recording equipment provided wonderful recordings. So many of the best recordings of that era both wonderfully lush, resolving and transparent, have to play some of this stuff every listening session. I often then segue into 60's, 70's era SS recording equipment era, quite a different perspective! And then further segue into digital recording era, yet another perspective. All have unique inherent qualities, yet they still retain difference and hiearchies within those eras.My take is a good system should be able to provide an engaging listen with most recordings from all eras.

I have long time friend, guy had first high end audio system I ever had the pleasure to hear, how I became addicted. Anyway, he eventually became audio engineer and now owns a sound reinforcement company. Over time he left audio hobby for the production side of business, great audio equipment morphed into great recording equipment. He's got the best of best of everything, I've been to a number of concerts he provided sound for, by far the best sound quality I've heard at a live show, and I've been to literally thousands of them. The few studio projects he engineered are also best of best. And this work with jazz, reggae, rock, experimental electronica, electronic dance music, many genres. If only all recordings and concerts were done with such care!!! Audiophile production people sure are rare breed, wonder why no audiophile has ever started a school or mentoring program for people wanting to get into audio production, Perhaps too old school a thought when home recording equipment so ubiquitous, and probably who you know rather than particular talents to work in recording studios.

And I've yet to be convinced that ever increasing resolving capabilities are detrimental to recordings of at least low side of mediocre. I play plenty of these quality recordings, some may even label them as poor quality, and they only sound better as the resolution of my system increases. I hear the warts, but the continuing and ever increasing sense of real live performers in listening room far outweighs the warts. And this not some new sensation such that the novelty of newfound resolving capabilities  has blinded me to the warts.

Since I"m solely into streaming these days, vast majority of upgrades in recent years have been in streaming equipment, and believe me, plenty of opportunities with upgradies in streaming. My digital sounds more analog over time so the added resolution has gone hand in hand with a more natural timbre, this makes the lesser recordings sound better on two fronts. I presume this two handed improvement will continue over time which means there would be no downside to increasing resolution. I should add, my system is not coloring or obscuring recordings in the least, my dac uses ESS Sabre 9038 pro chips, many would characterize sabre chip dacs as highly resolving and clinical. I hear the resolution, not the clinical. Point I'm trying to make is my system is not hiding warts.

I believe with the right combination of equipment the vast majority of recordings can be made to sound better with higher resolution. I'd hate to believe a higher resolving system would make more recordings unlistenable, I'd quit trying to evolve my system.