Probably the main thing I have learned is that I would prefer to get the sound I want coming in - because anything after that always seems to be a compromise.
You are of course correct. If there is such a thing as this so called "harmonic balance" that makes the "big time" records so desirable, I think it would be the result of recording some great arrangements of well-written tunes performed by some madly-skilled cats on great sounding, well tuned and maintained instruments. Of course, adding great technique by a skilled engineering staff to capture it is always a plus.
Some great equipment in great sounding rooms doesn't hurt either