The answer to your question is both yes, and no. Yes, because a campaign setting made 20, 30 or 40 years ago is obviously "more traditional" than one made a few years ago, because seniority and tradition go hand in hand.
Here's an interesting point - "old" does not mean "traditional". I went to see a movie on X-mas day, once, a decade ago. That does not make it my X-mas tradition. Traditional is the thing I
usually do, not the thing I
used to do.
I'm not saying we should go back to the old days of millions of splatbooks, I'm just saying that's it's been more than 2 years since the excellent Xanathar's guide.
Honest, and possibly rhetorical question - how many characters have you played in fullness in those two years? How many of the options of Xanathar's Guide have you really explored?
Heck, I haven't even played all of the neat Player's Handbook characters I'd like to try, much less fully explored Xanathars!
Do I need new, for the sake of new? No. I only need new for the sake of
using the material. And, by admission... until someone invites me to a game that calls for it, I don't really need new material to use. A friend just started up a game, and literally asked me to play an artificer. I didn't buy the new Eberron to do that - I'm using his, because I only need one class.
Meanwhile, we got 5 cross-promotion products, which I have no reason to buy.
Rick and Morty and Stranger Things are starter sets. Nobody who isn't starting has a real reason to buy them. Meanwhile, crossing with a popular property seems an excellent way to start people.
That leaves Eberron (hardly cross-promotional, is it?), Ravnica, Acquisitions Incorporated, and now Wildemount. All setting books. The fact that they are cross-promotional... isn't relevant. It is a setting book, and you have as much reason to buy it as any other setting book (either lots, or none, depending).