>Overall, I think the WHATWG structure, of being open to input from all (instead of pay-to-play),

Thats not entirely fair. The WHATWG is also pay-to-play in a way - the browser makers have disproportionally higher power, even more so than the w3c model where there is at least some form of consensus forming among a group of people with more international representation. Now technically anyone in the world can open a github issue (w3c also does it though now), but thats about what anyone can do to oppose something in the spec that the browser makers have their hearts set on.