Earlier quoted context omitted.
Firefox is spending millions on political goals, failed OS' etc. Only a small portion is put into the progress of FF - speeding up rendering a notable exception.
Ever since they forced out Brendan (co-founder and creator of javascript no less) because of their political intolerance, FF has really started to go down hill. Each release you have to go through more about:config settings to turn off all their "helper" apps (ie. spyware partnerships).
I'm sorry you weren't around when Firefox (then called Phoenix) was really good, but most FF problems pre-date 2014. They are actually being addressed just about now.