Mobile Firefox constantly gets bugged and stops rendering pages until you restart it. It also has issues with scrolling on some pages where it won't let you scroll sometimes. Github is notoriously bad, you can't read code if you can't scroll through the file. As a developer not being able to use Github is a deal breaker. The browser itself is also missing features like webgpu. While extentions are nice, the browser engine itself being this broken for years makes it a painful choice.