I'm not the author, but I recently gave up on Firefox, sadly.
Since I needed to keep around a Chromium anyway, and I already am forced to use one for work, it became simpler to just use solely use a Chromium.
In the process I dropped some extensions.
It's been great.
To be honest I find the use of a separate browser at work a good way of forcing separation - all "work stuff" is done in one browser, and all "personal stuff" is done in a different one.
This time around I'm using Chromium for personal stuff, and Firefox for work-stuff. I do more work-related browsing, so having the vertical tabs in firefox meant that was the better browser to use for official stuff.
(In my previous job I used safari for work, and firefox for personal.)
I used Firefox for 20 years, loved it, defended it. But they just kept removing features that I was used to, and I ran into some bugs with popular websites and decided to hang it up. Currently on Brave and fully convinced it's the new Firefox.