There are three sources of interference to the signal that finally reaches our ears, electrical, mechanical, and acoustic. While I believe acoustic is far and away the most significant detractor from the original signal, even if we reduce its contribution to just 1/3, we are leaving an enormous opportunity for improvement on the table.
Part of my motivation to make this a separate topic is to bring it to the forefront. It has been ignored too long and there are so many sound systems posted on Audiogon with wonderfully sounding and well-curated equipment that languish in a morass of bad reflections. Having room acoustics as a separate topic codifies its place in hi-fi and you ignore it not at your peril, but rather as a waste of money because you are not hearing what you paid for as well as you could.
Probably treating room acousticaly is probably best investment one can make in pursuit of best possible sound. Properly treated room with properly speaker positioning can make even modest equipment shine.