How to meaningfully audition speakers??

Frogmam,
Thanks for your very insightful perspective. You mention the engineers having less reliance on actual listening to the musicians play and are instead in the booth. This one factor explains plenty! This approach would seem to lead to fixing a product that requires no (or minimal) fixing or tampering. There's probably an overwhelming desire to utilize available technology and gadgets just simply because you can rather than true need.
I also agree with vyour point concerning microphones, it appears mutimicing is over relied upon and often does more harm than good. The simpler microphone use of the 1950s stereo era have clearly stood the test of time.
Charles,

It has nothing to do with analog vs. digital, specific mics, multi miking or even the experience of the engineers. There really is no simple answer and therefore no simple fix.

Basically it has to do with differing aesthetics. How a classical or jazz recording is supposed to sound is very clearly defined. For jazz it should sound like "Kind of Blue", one of RVG's Blue Notes, or maybe like an ECM recording. Because jazz has such a well defined sound there are a whole list of things you don't do when recording/mixing a jazz album. For instance you wouldn't use a non-lin reverb on the drums. No compressor on the bass. No vocoder effects on the vocalist. Don't shift the sax from the left to right channel during his solo. There are just things that you won't think of doing on a jazz recording. There are no such rules or prohibitions in pop/rock recordings. Because of this the sound of pop/rock recordings is very variable. For some engineers it's a case of too much freedom and the sound quality can suffer.

Ultimately, talented musicians working with talented engineers are more likely to make good sounding good music than other combinations.

Note that most musicians are surprisingly clueless about sound mixing regardless of their talent as musicians. The good news is there are zillions of great sounding recordings to enjoy, and some are new...Also you really can't "train" engineers to do anything but know what knobs to turn as recording esthetic is more in the "talent" or "art" genes and that quality remains mysterious. Example: A very well regarded female singer/songwriter came to play at a concert I was mixing (I designed the system and had been mixing this monthly concert series for years), and brought along a young dude she trusted to mix for her (a few higher profile artists liked to do this, and I usually don't mind at all since they're usually fine)...this guy was amazingly incompetent in every way, although he claimed to be a professional studio engineer. NO idea how to use trim pots for mic balance, no sense of the room sound...man...and this resulted in our first show EVER where people thought the sound kinda sucked. The end.

Well based on the comments it safe to say that sound engineers aren't formally trained like electrical, mechanical or chemical engineers. So it is a case of an art form/ practical experience rather than an established technical approach. I'm coming to the conclusion that the folks recording jazz are just using their ears(more often) and have more talent and concern regarding the sound quality of their work. What other explanation is there? This genre's consistently good results aren't by accident or random chance.

Some great things here - first, I knew that Frogman would write a much better response than mine, and I am pleased to see it does not conflict whatsoever with mine, either.

Charles, I believe his post answers your next question to me, I think?

Bifwynne, I think that is a good point you make. With digital editing techniques as they are now, an engineer who knows what they are doing can pretty much make anything sound like whatever they want. This is another big reason why there is not much standardization.

Onhwy61, while I understand your point, I have to disagree. Unfortunately, one thing Frogman and I are basically saying is that there is not much aesthetics involved at all in recording nowadays, particularly the really commercial pop stuff. I think you are giving the engineers too much credit there. As Frogman said, recreating subtle tonal colors and balances of acoustic instruments, no matter what the ensemble size, just cannot be done artificially with multi-miking and a mixing board. So yes, those things do matter very much in the equation. Multi-miking and mixing tends to almost completely obliterate spatial cues, for just one example. That's why they add reverb, to make it sound more "live" again - but all sense of the actual recording space (assuming it was in a decent concert hall or jazz club or church) is gone, and with it many other important aspects of the sound. This unfortunately applies to all but a very tiny percentage indeed of the digital recording that has ever been done, so that does have quite a bit to do with it, too. This is not to say that you can't mike things for a digital recording the same way for an analog recording - you could. But this is almost never done.