We made the decision several years ago to integrate Servo components individually rather than trying to replace the entire engine (for the reasons outpost in the blog post linked above).
We invest a lot in Gecko though, precisely because it's important to have a world-class independent engine.
It performs very poorly when there is a lot of DOM content and js manipulation (think a kibana search+visual) and FF is notorious about memory exploitation. I was hoping replacing everything with rust code would be a start. A rewritr of gecko in rust at least. I don't have any workload at all that works better on FF and many of the ones I need to work smoothly don't.
But I completely understand why you wouldn't want to "boil the ocean". That said, I hope you appreciate how much support FF has from users. Anyone of us left using are doing so by paying a price for it. Everything else mozilla does appears like distracting side-quests. I would not care much about donating for wikipedia but if Mozilla focused on their flagship product more I would be happy to contribute both financially and through bug reports and grunt work PR's.
We invest a lot in Gecko though, precisely because it's important to have a world-class independent engine.