This sounds myopic, or what do you mean? W3C is not only about HTML and CSS innovation, but is responsible for and/or involved in a diverse set of relevant standards — many of which "big companies" don't show as much interest in contributing to.
https://en.m.wikipedia.org/wiki/World_Wide_Web_Consortium#St...
The DOM is largely abstracted over by JS frameworks and component libraries.
XML, XPath, XHTML, SOAP, etc gave way to haphazard JSON that's easier to use.
JSON-LD is a tiny niche and mostly unknown.
SVG is used only trivially as a PNG replacement or for vector graphics interchange, while Canvas is more common whenever performance matters.
Aria is mostly an afterthought, put in at the last minute with alt tags and roles on random elements.
Maybe MathML is still used on Wikipedia?
Can't comment on the other ones I've never heard of, but the web ones all seem either dead or niche.
I think this illustrates what I meant by irrelevance. It's not that they make bad standards or have bad ideas, it's just that companies have always preferred their own implementations of these ideas rather than some standard. Over the last two decades, the W3C has been at times a strong suggestion, at times a weak consideration, but never an actual standard. It was always the big tech companies making the actual standards. We were lucky when a W3C spec actually reflected real world implementations.
And this isn't just my opinion... the WHATWG was created specifically to bypass the W3C on purpose.