As someone who has built and lightly studied Firefox codebase out of pure curiosity this technical joke doesn't really ring remotely true. Sure it's an older codebase and Mozilla doesn't have enough funding manpower to do big rewrites but I don't remember Firefox crashing on me in recent times and I use it exclusively on Mac/Linux and Windows. No site compat issues either. So stop blowing smoke I guess and provide actual details on how it is a joke?