Wow! I have maybe a dozen extensions installed, but even on my work laptop (which is not very high spec), I can use Firefox easily within 10 seconds of opening it. Do you have tons of tabs open and have it set to reopen the previous session? I'm kind of shocked to hear that it could take this long
Might be different if I did not have an SSD (from 2010) of course.
Edit: I should note that Firefox is only slow on the first opening after a cold boot. Firefox is fine after that. Might be some caching issue.
Edit 2: After a cold boot, Firefox loads quickly in safe mode. Disabling ABP did not seem to eliminate the problem. Disable NoScript seemed to help a bit. I might switch to uMatrix instead of those two and see if that helps.
For reference, re-installing FF doesn't seem to fix it, and I have neither NoScript nor uMatrix installed (although do have uBlock Origin).
(I've been meaning to troubleshoot it for a while, and if I manage to track down the issue, will let you know).
It either loads in matter of minutes, or it displays last seen cached view... and loads in matter of minutes.
Still - the latest update to gmail was basically a downgrade from user perspective. It is slower, and looks the same and offers no new functionality.