Microsoft just did whatever they wanted with the web "platform", and so will Google.
In Microsoft's case what they wanted was nothing. They weren't a web business, saw it as a threat to their platform leverage, and so just left it abandoned and stagnant for years.
Google is simultaneously better and worse: they won't leave it stagnant because the web is their platform, but on the other hand they have a lot more to gain by abusing control of it.
We already have a number of Chromium based browsers that go against some of Google's most fundamental interests (e.g Brave).
Costs matter, and Web development costs are high. Google benefits from coordination, funding, and one migh presume, cost advantages, which would be exceedingly difficult for any comparable US or EU effort to match.
Development in lower-cost-of-living regions, perhaps most viably China, might pose an alternative.
That's where Firefox is right now, unfortunately.