(FWIW, I don't give a crap about up/downvotes, I want to engage in a deep discussion.)
Back in the day when it was FF vs. Microsoft Internet Explorer the need for a competing FOSS browser seemed very compelling, but I don't think FF won marketshare on that, rather it won on merits: FF was better than IE.
Today the situation seems different. To me it seems to make sense to let the engine become a standardized component (developed FOSS-style) incorporating work by Google for speed, security, and reliability, and let the diversity and competition happen on a higher, more user-facing level, in terms of policy and politics and UI/UX and so on.
If people wanted features, why was Opera always so niche? It used to be so far ahead in features. I guess Brave today has quite a few features. Maybe Vivaldi.. I haven't looked really.
I think the real issue is that the vast majority of users don't really care about browser features beyond a certain point, a point which all modern browsers have easily covered. You could sit a person in front of Chrome, Firefox, Edge, or Safari and they'd barely notice. If there's attachment to a certain brand, it's mostly emotional. Arguing that people should use X over Y is like arguing that they should drink Pepsi over Coca Cola..
It's hard to differentiate a browser in such a market. It's just a window to the web, with tabs and bookmarks and a handful of features. And an adblocker extension, for some 30% of users. Beyond that, it just needs to work and be fast.
Back in the day when it was FF vs. Microsoft Internet Explorer the need for a competing FOSS browser seemed very compelling, but I don't think FF won marketshare on that, rather it won on merits: FF was better than IE.
Today the situation seems different. To me it seems to make sense to let the engine become a standardized component (developed FOSS-style) incorporating work by Google for speed, security, and reliability, and let the diversity and competition happen on a higher, more user-facing level, in terms of policy and politics and UI/UX and so on.