At the end of the day, what difference does it make why so few players use feats? The point is, very few players use feats. Full stop. Examining 8+ level fighters is such a tiny subset of all characters that it's useless. Even though fighters are the most popular class, they still only account for about 10% of characters. Limiting ourselves to 8th level plus makes that number even smaller.
Whoopee, 6% of players use feats regularly. That's what's been said all the way along. There's a solid number of those who use feats, but, it's hardly a large one. So, we get three pages of feats in 6 years. A nice bone for those who use feats, but, not much else. ((And I say this as someone who uses feats and almost never maxes out a main stat - the difference between +4 and +5 doesn't matter in comparison to what a feat can do.))
Getting tied up in knots over whether tables use feats or not doesn't really matter. The upshot is feats aren't being used.
Would I love to see a maneuver set for fighter types? Sure. Is it going to happen? Not a chance. Again, there just isn't the demand for it. FIghters only make up about 10% of all characters, and battlemasters are less than half of that. If there was this big push for maneuvers in combat, wouldn't the Battlemaster be a lot more popular than it is? Battlemasters make up only 2.5% of all characters on D&D Beyond. That's it.
Again, no one is able to provide anything even remotely like evidence to support these claims. At best, we have gut feelings and reading chicken entrails. Meanwhile, the game continues to break every possible record out there.
So? And?
The point I'm making is people shouldn't be making false and disingenuous claims.
Unfortunately you decided you needed to add to those, with the bolded bit. That's absolutely not something you can claim based on the DNDBeyond "data". We simply don't know the following:
1) How many people play characters who have at least 1 Feat.
2) How many people play characters who they intend to have at least 1 Feat, as they level.
3) How many groups "allow" Feats.
We just have no idea.
So you claiming "very few players use Feats" is just disingenuous nonsense. It's exactly what you seem to be trying to complain about. We don't know how many DNDBeyond PCs are even actually played. As a bit of anecdata, I can tell you of the 25+ PCs on my account on Beyond, only 5 have ever been played. I know one of my players has far more and only 3 of his have been. As there's no way to tell, we can say whether the ones who actually have Feats are being played or are merely theoretical. Hell, based on DNDBeyond data, we could assume anything from 0% to 100% of groups allowed Feats. But it'd be an assumption, and the bolded text is just an assumption. If you genuinely believe it, you don't understand the data or what it means. If you're using it as a rhetorical talking point, it's disingenuous.
As for "hardly anyone plays Battlemasters", again, we have no idea. We can say what percentage of PCs on DNDBeyond are (or were, at a specific point in history), but are they being played? Not played? It's impossible to say.
You and Parmandur should both stay away from making claims about whether Feats are used or not. The best evidence we have comes from WotC continuing to support them in Tashas and in making the Dark Gifts in Ravenloft swappable for Feats. As Parmandur says, they're significant enough that WotC thinks they're worth space in their books.
Whether the game sells well or not does indeed likely have little to do with the presence or absence of Feats, but I'm not sure if that statement is just boosterism on your part or you think it has some implied meaning.