> And even when Microsoft eventually caved and started the Edge project to create a compatible browser, they ended up admitting defeat and pivoted to Chromium themselves.
This can be interpreted as a problem of marketshare not staying balanced. It may have shifted hands, but the imbalance is the problem -- if Chrome had to deal with making changes that would be incompatible with half the users that visit sites on Chrome, they'd be forced to think a lot more about it.
This doesn't mean they can't add value in the form of non-standardized extensions -- that's not a desirable goal because it would stifle innovation. The point is that at some point if users are on browser Y and they get a "this site only runs on browser X", they're just not going to visit that site, and developers are going to shy away from using that feature. In a world with lopsided marketshare, there's not much incentive for the company with the most marketshare to be interoperable.