Well... I do understand... that master analog tape has the best sound quality, followed by vinyl, and then possibly HD CD’s / files, WAV CD’s / files, FLAC files, and MP3 files (or variations of all of these).
But... in my A/B comparisons the only ones that present an easily discernable difference are the analog recordings vs anything digital. I have a bit more difficulty discerning the difference between WAV and FLAC files (almost can’t tell the difference at all - may be imagined), but I can tell the difference between FLAC and MP3 files (the resolution of the FLAC files or WAV files compared to MP3 is noticeably better) - on most systems, even car audio systems. Though, the difference is much more noticable on my high-end systems. However, I would note that I have several MP3 files that have great sound quality on these systems, which have caused me to wonder if the WAV or FLAC or HD versions of the same music could sound that much better.
And... yes... the recording technology and techniques in recent years have improved dramatically over those typically representative of the 80’s and earlier. The "close-miked" techniques, etc., etc. have markedly improved the resolution, dynamics and realism of more contemporary recordings.
But, for just listening to background music with inexpensive systems, even though some of those have incredibly good sound quality, MP3 is fine. Thus, In that context, I’d bet very few would not be surprised and pleased with the sound from, as an example, a lowly Echo Dot and the Brookstone iDesign Wafer CD Player with NXT Flat Panel Speakers w Subwoofer, or the Mini-Maggies with Bass Panels. Quite surprising... really - when considering only modest volume background music.
Although, when I take the same Echo Dot and plug it into my the back of my ARC Ref 3 preamp, and play it through one of my high-end systems... the sound is terrible... poor resolution, and clarity... poor dynamics, etc. So, there are evidently many more factors that produce high quality sound than just whether the system is "high-end," or not. And... yes... I'm sure the fact that the system is better, is a factor in how those MP3 files sound... just not the only factor.