[LordLestat]

My personal reason not to use Pale Moon - and instead Otter-Browser. I also would recommend Vivaldi more than Pale Moon.

If you are creating a browser it is pure illusion to think you can also handle engine stuff. That is such a complex matter - HTML5, CSS3, ecmascript - Take a look in the past. Moonchild, Tobin and the others had to re-base Pale Moon to be able to be compatible with today's web.

And now that should be possible when they are basically just doing it another time? Stuff does not stay complex, it gets worse the more time is progressing.

And if they have been unable to implement promises or shared array or whatever on their own.. how they actually could believe they can implement upcoming features?

If you are forking something, make sure the engine work is done by someone else. That is the only valid way to get stuff done and not becoming outdated.