Chromium based ones are at the mercy of Google. Firefox, however, is independent in that sense.

When google decides to drop support for manifest V2 (which is the one unlock origin uses), every chromium browser drops support for it. Unless they make a fork of chromium and add manifest V2 back in. Which means extra effort every time they want to update with upstream, since there probably will be merge conflicts.

Firefox can just not drop support for it, literally 0 effort.