All I know is neither 3E nor 4E satisfied my need for flavor. Key words for me do nothing. Too much crunch, is also a problem. I like nice and easy rules, with a good deal of inspirational flavor that makes me want to play the game and gives me ideas. I am not thinking of 3 page spells so much as the Van Richten guidebooks, many of the old historical sourcebooks and kit information from the complete books. The Complete Bard for example greatly enhanced the adventure and rp content of my 2E campaigns. I didn't get that from the later complete books. And nothing like Van Richten was ever released for 3E that I could find (at least not by WOTC).
Well, I won't disagree that little in the way of 4e material has the sheer verbosity of things like the Complete Fighter or Complete Thief books (I don't have the others around so I can't comment, but I assume they are similar from what I recall). Still, a lot of it IS crunch. I mean its VERBOSE, and there are certainly pages and pages of fluff, but there are pages and pages of crunch too, often pages long simply because it has to explain everything in detail since 2e lacks a lot of 'hooks' for things like maneuvers or standard ways of doing things. It seems like the fluff factor could have been higher if the rules had been more clear.
If you look at the core 4e books and the core 2e books, the 4e books have actually about the same amount of fluff as 2e does. I do see quite a lot of story ideas, background, and other fluff in the 4e supplements too. I don't know why people insist that 4e is bereft of this stuff, it really is not. There are also 4e books that are very much like the complete books, though organized differently. For instance the Tiefling and Dragonborn books. Notice that WotC discontinued making those sorts of books because presumably they sold poorly.
So, yeah, I would agree that few 4e supplements have the fluff to crunch of the Complete books. There are 2 questions I'd ask though. 1) Did TSR actually sell those things in enough numbers to make money? I remember them sitting on book and game store shelves for literally 10 or more years. My FLGS literally STILL HAS a small section of shelf in the back of the store with a full selection of 2e supplements, new stock. 2) Could WotC make money selling that kind of supplement? Note that it is not going to really matter what rules are currently in vogue, 4e, DDN, whatever, such books are going to be largely the same either way, right? Its hard to see how if they didn't sell 2 years ago they will sell next year or the year after.
PERSONALLY I'm happy to read some fluffy books. OTOH I have read my 2e fighter, priest, and thief books, and a couple others, through a couple years ago and the fluff is still just as useful now as it was then. I'm not sure these need to be system books. I can see why WotC would want to tie them to an edition, but OTOH I'd prefer to have good high quality material that is system neutral. Honestly, while I found good game ideas in the TSR stuff, I think you can today find VASTLY more accurate, complete, and interesting material on cities, castles, ancient civilizations, Medieval Europe, etc etc etc in non-RPG focused resources. For instance I ran a fanciful game of knights and maidens in distress etc a year or two ago and I found a vast amount of material about medieval romances, as well as translations of all the source material. It was great, and no RPG guide on the subject would come close to providing the same level of material.