I agree that in most cases a well mastered cd quality is the highest quality we can hear though.
CD is a severely compromised and outdated format. It was designed in a long bygone era. The design criteria were, it should be a disk. It should fit into a car stereo head unit. It should contain as much data as possible. Well that was the stone age. These days we can, and should have access to far higher quality files than what is available from a CD. We can easily store far more date in far less space than we could back then.
How can hi res be better than a CD? Dynamic range, instrument separation, sense of space, etc. These all improve, but ONLY if your system is good enough to show these differences.
Why do we still seem to be stuck in the CD resolution age?
1. Most people do not have a system that makes better then CD quality worthwhile, so they just don't care, and will not pay more for hi res.
2. The recording industry is a total and utter mess, with a jumble of middle men, that all want a cut, and all have a deadly fear of a simple system that will allow consumers to buy what they want, artists to be paid and the main recording company taking their fair share. The hysterical copy right protection and regional protectionism has hamstrung development. For example, I can't get Tidal, because I live in the wrong part of the world! Of course I could circumvent their silly protection but I just can not be bothered.
3. An unhealthy and unproductive focus on home theatre with people spending money on a disorganized mass of cables, speakers, amplifiers and processors that has taken the impetus away from real improvements in audio quality.
