And some of these proposals are available as polyfill browser extensions for Firefox

That's great from a user perspective, sure.

From my perspective, with all of these different web APIs, I imagine Mozilla are walking a tightrope: if they refuse to implement all of them, there's a good chance that websites will ask the user to use Chrome, pushing it further into obscurity. Go too far, however, such as implementing Google-driven proposals like Topics, and you weaken the privacy advantages of the browser.

I'm glad that they take both a moral and technological stance here - someone needs to.