The moment they acquired an ad company (Anonym) the writing was on the wall where they were headed. Someone needs to pay for all the... interesting side projects they've got going as well.
By the way, it would be wonderful if you or someone could link to detailed instructions (or maybe even just a script you can run or something) about those tedious about:config edits.
Arkenfox has a good user.js [0] you can use. Each comment tells you what the option their disabling is.
I had been putting one together based on it for newer machines (and it worked great), but just now when I went to look for it, I'm not sure what happened to it. Sorry I can't share mine.
If I recall correctly, you just plop the user.js into your profile. You'll want to do it from a fresh profile* and then any time you want to make a change, you'll make it in user.js instead of about:config. What I believe happens is every time Firefox start, it applies all the configuration options specified in your user.js.
To be honest, the writing was on the wall way earlier; when Mozilla integrated Firefox Sync (unless you sync to your own server, ofcourse: https://github.com/mozilla-services/syncserver) and more recently the acquisition of Pocket in 2017, after a 2 year partnership.
Data mining gold galore, not unlike Yahoo's acquisition of the "free" Delicio.us back in the day.
With the being said. Firefix does make it pretty easy (but not obvious, requires some tedious edits in about:config) to disable most of their spyware.
Tor browser, ungoogled chromium are good choices. Other see reddits such as https://www.reddit.com/r/browsers/comments/11by0m7/what_is_t...