1 - the native browser being an old firefox/gecko fork embedded into their own UI framework, giving a poor performance and dated compatibility quirks 2 - the android emulating runtime meant that you get again, dated , poorly performing android apps, that you're driven towards because the browser engine was so poor.

these two mean you basically end up with a sub-standard android handset/UI, and a tiny market for native app development (because everyone made do with android), its a real chicken/egg.

In fairness I've not used it since the sony XPeria days, but it was my daily phone for 3-4 years since the Jolla 1. It was cool being able to emacs and irc natively on the phone, but that was limited in use cases tbh.