It's what got me off FF for a long time. I stuck around on FF 52 ESR(I think?) for ages, the last version to work with pentadactyl.

Then I finally switched to Chrome because it was much faster than FF and my extensions were dead anyway. I switched back a few years ago because FF became good enough again. I wouldn't be surprised if others did the same (and possibly didn't switch back).

When I switched, everyone I provided tech support in my family for also switched. I did not switch them back because I don't think it's worth inconveniencing them at this point.

Obviously my case is a miniscule amount of people, but it wouldn't surprise me if the story wasn't somewhat common.