> Mozilla has always been under-resourced compared to the competition (IE, then Chrome) and taking people off improving Firefox/Gecko to work on embedding never made the cut.
Yeah, sure, imitating your competition is the right way to handle that. /s
Moving away from the unsustainable XUL extensions model ("no stable API boundary, just feel free to poke the internals of Firefox any way you like") was another piece of architectural churn that had to happen.