With that said, almost all of Mozilla's revenue comes from Google, which might possibly influence what features they implement, their stance on various web standards etc.
They all tend to lag behind over time, until the fork is eventually too old and it's either abandoned, useful changes I was relying on are dropped, or becomes just too old compared to upstream to be fully compatible (and thus just annoying to use).
Just the burden to upkeep the upstream changes, in either firefox or chrome forks, seems to be significant enough that I'm quite pessimistic on the lifespan of these projects.
You might just as well do your own thing, and don't pretend to be a mainstream browser replacement altogether.
But long term, I would much rather see a truly independent open source browser engine.
Unless you’ve got some examples to back this up, it’s FUD. Posting hypotheticals is how rumours start, and this is just stirring the pot.