(Mozilla employee, though not working directly on mobile)

Mozilla is invested in Firefox on Android for the long haul. We landed a complete re-architecture this year (Fenix). It hasn't been completely painless -- for example, as you seem to have experienced, we've had to split our development time between working on the new engine and maintaining the old -- but Fenix is already better than Fennec in most ways and is significantly easier to improve moving forward.

https://blog.mozilla.org/futurereleases/2020/01/17/a-brand-n...