These right there, and all the other issues in the same vein are the probably the reason.
Sure, make a simplified browser interface by default. But don't forget to give power users an escape hatch to get more control over the browser, and make it do what they want. They are the ones that recommend the browser to other users.
Here's what one of Firefox's Android developers thought of users after they raised concerns over the abolition of extensions and the rushed, buggy and inferior release:
https://web.archive.org/web/20200731235001/https://twitter.c...
Meanwhile Mozilla's CEO continues to fleece increasing millions of dollars while being responsible for a massive collapse in market share (she increased her pay 400%, while destroying the company).
https://news.slashdot.org/story/20/09/23/1528219/firefox-usa...
https://blog.mozilla.org/en/mozilla/we-need-more-than-deplat...
https://www.ghacks.net/2021/03/14/mozilla-plans-to-remove-th...
https://www.ghacks.net/2020/04/08/how-to-restore-the-old-fir...