Yes, Firefox/Gecko is much more one thing, Mozilla apparently even had some problems with that close integration and baked-in assumptions when building the Android variants.
Splitting this out a bit more seems like it would be a good strategic choice, not just for Mozilla, but for the web in general. There are undoubtedly all sorts of technical challenges involved, but betting on only Firefox is putting all eggs in one basket.
Say what you will about Blink/Google, but the easy with which you can build a browser on top of it has spawned a plethora of browsers, ranging from Edge and Vivaldi, to all sorts of more niche ones like Otter and Qutebrowser, and many more.
Half of Vietnam is using Cốc Cốc. Yandex Browser is fairly popular in Russia, UC Browser is popular in China (or rather was, since it was banned) and some other Asian countries.
There's no reason at least some of these couldn't have been a Gecko-based browser.
Yeah, for smaller projects with only a handful of people behind them, WebKit (via WebKitGTK) or Chromium (via QtWebEngine, Electron, Chromium Embedded Framework) are pretty much the only choices there are. The only exception maybe being Pale Moon.
For browsers which are based directly on the Chromium codebase without being supported by Google, there are definitely many more resources needed - I don't see a particular reason why those couldn't be based on Firefox either. From what I see in QtWebEngine, keeping up with Chromium isn't exactly easy - IIRC they said they need about a person-month to catch up with a new Chromium release, usually with millions of changed lines.
Say what you will about Blink/Google, but the easy with which you can build a browser on top of it has spawned a plethora of browsers, ranging from Edge and Vivaldi, to all sorts of more niche ones like Otter and Qutebrowser, and many more.
Half of Vietnam is using Cốc Cốc. Yandex Browser is fairly popular in Russia, UC Browser is popular in China (or rather was, since it was banned) and some other Asian countries.
There's no reason at least some of these couldn't have been a Gecko-based browser.