Mobile browsers aren't sufficiently differentiated enough for a significant amount of people to bother changing the default. Does anyone really think Samsung Browser would get close to 1.6% if it were a free and unbiased choice?
Apple sets the rules, gets special access (new releases, features, platform changes, countless other things), and relentlessly captures their users into the Apple ecosystem/moat. You seem to think swapping the rendering engine is a trivial task but you're asking them to practically create a new browser. And for all that effort, you're still competing with an opponent that's basically cheating. I'm not sure why Firefox/iOS even exists, frankly.
Apple sets the rules, gets special access (new releases, features, platform changes, countless other things), and relentlessly captures their users into the Apple ecosystem/moat. You seem to think swapping the rendering engine is a trivial task but you're asking them to practically create a new browser. And for all that effort, you're still competing with an opponent that's basically cheating. I'm not sure why Firefox/iOS even exists, frankly.