At the end of the day, they failed at their original mission:
"It was intended to harness the creative power of thousands of programmers on the Internet and fuel unprecedented levels of innovation in the browser market. "
All of the innovation on web standards, web frameworks, etc. has been coming from FAANG and Mozilla is funded by them. They defocused and have been messing around with all kinds of other stuff.
Not all of the change on web standards has been good or appropriate innovation perhaps exactly because of Firefox smaller clout nowadays. Look at the story of Mozilla's H264 implementation and you'll see it's clearly Google that has managed to throw it's weight around and decide what would become the standard whether it was good or not.
I think their stated mission was different than what motivated the original developers - killing IE. Once that was basically done, things started to defocus.
"It was intended to harness the creative power of thousands of programmers on the Internet and fuel unprecedented levels of innovation in the browser market. "
All of the innovation on web standards, web frameworks, etc. has been coming from FAANG and Mozilla is funded by them. They defocused and have been messing around with all kinds of other stuff.