I believe all derivative forks of Firefox (waterfox, arkenfox, librewolf, zen) are dependent upstream on Mozilla for engine updates.
So, in a way, all the FF forks are still at the mercy of Mozilla.

The only independent browser written from scratch is Ladybird, with a planned stable release in 2028.
Early development appears to be promising.

There are 3 main browser engines right now :

  • Chromium (Chrome, Vivaldi, Brave, Edge, Opera, Arc)
  • Webkit (Safari, Orion)
  • Gecko (Firefox)

Firefox reached its peak market share of 32% in 2009 (before Chrome became dominant).
Right now FF's market share is only at 2.5% as of early 2025.
In other words, Firefox lost almost 93% of its market within 16 years.

Out of these 3, Firefox has the lowest market share right now (it was not like this many years ago).
If the open-source community ditches it, then FF's market share will be almost negligible and Mozilla may be further dis-incentivised to develop it further.

Web-devs nowadays probably only test their websites against Chrome and maybe Safari, Firefox is probably an afterthought for them.
In the near future, 'heavy' websites requiring fanciful or custom user-input / output may cease to work properly on FF, already this has happened.

Zen is one of the most-starred open-source browser project on Github right now, with active development.

    snowee forgot about all the webkit browsers. they usually very fast but behind on thins like addons/extensions etc,

      snowee In other words, Firefox lost almost 93% of its market within 16 years.

      thanks Mozilla for ruining Firefox 😠 💢

      snowee There are 3 main browser engines right now : Chromium (Chrome, Vivaldi, Brave), Webkit (Safari), and Gecko (Firefox)

      Firefox has still advantage of supporting MV2 extensions like uBO over other chromium browsers.