In sci fi, black box Traveller is pretty much a quintessential old school game in mechanics, style, and presentation.
That's because Marc Miller and crew analyzed what made the original D&D set tick, so I understand the utility of such examination. Ken St Andre did a similar but less in-depth analysis (based on a brief reading of the booklets, IIRC) , and was the first to market with something meant to be "D&D, but better" (by some measures). So, it's no big surprise that many fans of old D&D find similar qualities in those games. There can be some reasonable basis for saying, "Hey, if you like this game, then you might also like that game" -- but that's a
long way from a guarantee.
The
same set of characteristics is not present in
all such games. Most lack, even broadly, features considered essential to D&D. In stricter terms, they clearly
are not D&D. Moreover, there are features in some that many "old school" gamers would object to seeing added to D&D. It might not be such a big deal if someone goes along such lines with "house rules" -- but to inject them in any "official" sense might be offensive. At best, it would depend on details of implementation.
The "school" may initially have coalesced in reaction to developments of the 2e era. There certainly are some folks who basically anathematize all that is "post-Gary" (and a subset of them who consider
Unearthed Arcana the Satanic Verses). However, what really brought it to prominence was people finding that they couldn't stand WotC's D&D ("3rd edition").
Talk about your troubles with definition! The new meaning of "D&D" is simply whatever the heck gets labeled with the trademark. That's as arbitrary and capricious as you can get. As a consequence, 4e can be (by "old school" lights) "better" in some ways while being in sum if not "worse" then at least still so bad that the improvements hardly matter.
All this is significant
because the game is called Dungeons & Dragons. If it were "the latest edition of
Everquest", then maybe it would be in for a critique from "old-school" EQ players; but there would be little reason in the first place to expect much notice -- much less approval -- from fans of old D&D. What do most WoD, GURPS and Rifts players think of D&D 4e? Probably quite literally
not much. There's no "edition war" because in that context there's no pretense of considering different editions; they are unambiguously labeled as entirely different games.
Some things may fit the bill when implemented one way, not when they work another way. Some things may be acceptable to "old-school" fans in games that are not D&D, but it does not follow that they want them in their D&D. Start saying, "well this is old school, and so is that" in terms of different games, and I guarantee confusion because there are plenty of people who
want confusion. They don't want to understand what people are talking about. They just want some rhetorical way to claim the "old school" label as prize.
Maybe one reason is that there's pretty much a one-way street here. The fans of old games are not going through contortions to get them recognized as "new school", so there may be a supply and demand thing going on with valuation of the terms. Anyway, the business is certainly not symmetrical.
Hypothetically, though, let's suppose that some publisher of a "retro-clone" (or of the next edition of Tunnels & Trolls) decides to grab "new school" as a marketing concept. "We've got your 'play style', baby! Anything 4e does, this game does better!"
The fact would remain that it is actually different by design. People purchasing it with misleading expectations would probably -- and quite naturally -- be disappointed.