From hacking with XUL at around that time too, it could have been a contender if Mozilla had made more effort to document and promote it. The developer experie

From hacking with XUL at around that time too, it could have been a contender if Mozilla had made more effort to document and promote it. The developer experience was like “oh this could be cool to build in XUL” … spend some frustrating days scouring the code of different Firefox extensions to figure out how to do anything … produce an ugly UI that barely serves the purpose … realize XUL was completely unsuited for the purpose.