Feature with hundreds of requests gets shunned away. And things that people heavily opposes gets in just to be like chrome.
All the last features on firefox were corporate driven. Bookmark system by pocket. Video chat by Telefonica. Sync goals was probably to make their ad share revenue grow as now you are a logged in user. etc etc etc
Their most well paid dev is a javascript advocate!
Chrome gives you much less control of the web, but everyone uses not because it is fast, but because firefox is getting behind on everything. While the owners arguee about UI changes instead of doing what was successful in the past: put the patch someone already provided as an option and release!
the only interesting thing coming out mozilla nowadays that can change the world is fennec. the mobile version. But last builds on android cannot be completed without google proprietary apis anymore. and usability is crap now that they are trying to "fix" image viewing, which mind you, wasn't broken, it was just different than chrome.