> Just saying, there used to be real technical ammo to bring to the table

You're right, but those are 2 different discussions. On the one hand, why did Firefox stop being a relevant web browser in the general consumer base. On the other, why did it stop being so great for advanced users. There is some connection between both, of course, but...

Not even all technical users who were promoting Firefox originally actually did use that many advanced extensions. Even if you or I may think FF went to shit, for most even FF advocates, it didn't change that much. That's not why they stopped promoting it.

For me, personally, it was losing Pentadactyl. I'm using Vimium now but it's not even close. I'm still mad about losing that.