They can start by supporting more standards. It's getting harder and harder to view any modern site on this engine and the page load times are insane when compared to a Chromium stepchild like Vivaldi
Is it? What website can you not view in Firefox today? I almost exclusively use Firefox on my computer (Safari on mobile), and can't remember the last time I encountered a website that wasn't viewable in Firefox. Even my bank, which tends to be whiny about what browser you use, works 100% in Firefox too, even with all the warnings.
Seriously? Have a few concrete examples to back that up?