Which seems like a
wild stance to me, but
I'd say there's no "seems" about it. It
is a wild stance. Bonus actions serve a vital function, just as their predecessors, Minor and Swift actions, did. Sometimes, you want to be able to do a thing as a ride-along thing people can attempt to do, but you don't want to allow 17 different ride-along effects. It's extremely useful to be able to say "this is something that happens
around your Proper Action, but doesn't take up your whole ability to do stuff."
Doing it any other way creates enormous headaches and needless complexity. Are Bonus Actions more complicated than simply not having them at all, and nixing anything that would need such a thing? Yes, of course,
doing something is always going to be more complex than
not doing anything at all. But it is a very small step up in complexity, in exchange for simplifying a BAZILLION other things that would've been horribly clunky and ugly.
This just gets to the heart of my criticisms of the hyperminimalist design stance. That is, just as it is true that "less is more" sometimes--that is, you can
occasionally make gains by making do with fewer components--it's also true that sometimes
more is less, that is, by adding just a little bit of complexity in one space, you can eliminate ENORMOUS amounts of complexity in a bunch of other places. Removing the Bonus/Minor/Swift action would be penny-wise, pound-foolish design--and if Mearls cannot recognize that, I need to re-evaluate my already not-super-great opinion of his design chops.
Incidentally, I personally think the preoccupation with bending over backward to emphasize that Bonus Actions aren't required is silly. The simpler way is to give everyone a really obvious, basic, but useful Bonus Action they can always fall back on if they don't have any other option. BG3's "Prepare" action (specific to greataxes) is a solid option, just make it add (say) half your proficiency bonus to damage on one single damage roll you inflict during the turn, rather than every hit. Instant useful bonus action, modest but clear benefit, very straightforward. "When in doubt, Prepare; but if you have some other use for your Bonus Action, you probably want to use it."