And this is exactly what happens if you don't have something as part of the core rules structure. You've rather directly proven my point. If feats aren't part of the structure of the game, they're at risk of becoming a memory, which will leave the many many many fans of feats quite screwed.
lol. Cool! I can do that too!
"And, you've proven MY point. There are many fans of D&D that are screwed because they don't like feats, therefore, feats should be left optional!"
See how silly that sounds as an argument?
Imagine a group who finds themes far more interesting than feats. But, damnit, they keep coming out with feats! We're getting screwed!
Nah. I mean, why not build a solid foundation, that's simple, elegant and functional - and then build upon that with ideas that work (and maybe don't work). And, you're not left creating 4,000+ aspects of the game [feats] that are largely irrelevant.
Addendum: As RJS said, most of them are covered by other territories in the design now. Feats are just an imported artifact from an old design philosophy (and one I personally find makes the game far more "fiddly" than necessary to be compelling and complex).
Instead, devote resources and time to new ideas or fleshing out ideas you've published that fans are clamoring for more of.
Yah dig?