Why is Firefox's slow decline a bad thing? Firefox seems to be leveling out at 5% of users. Perhaps serving those 5% of users is more important than selling out

Why is Firefox's slow decline a bad thing? Firefox seems to be leveling out at 5% of users. Perhaps serving those 5% of users is more important than selling out and becoming another Chromium-based browser? Sometimes I think open-source advocates have an obsession with "winning" and think that increasing market share is the only goal. (You can also see this in the way that this article throws Brave and Vivaldi under the bus... lol)