FF is plenty competitive on the technical and feature front. It's market share is not a reflection of technical merit.

What's more, next to Linux itself it is maybe the only case I can see where a major piece of user facing software is kept competitive with the Apple/Google/MS tools.

LibreOffice or Nextcloud are technically far further behind Office and Google's online offerings.

Which therefore begs the question: Who else is in a position to do this?

At first glance, Moz with Firefox + a suite of self-hosted team and productivity stuff that works well in Firefox would make a ton of sense...