If all you’re doing is “unchecking” then there’s more you’re missing:
https://github.com/K3V1991/Disable-Firefox-Telemetry-and-Data-Collection
The whole advanced configuration settings in about:config are probably never seen by the majority of users. Ultimately though, you’re right: for the most part, privacy-focussed forks aren’t offering anything that you couldn’t manually configure for yourself in mainline Firefox, assuming you have the time, energy and interest.
Certainly, if you’re in the habit of policing all of these relatively undocumented flags with each update to be sure you haven’t been opted in to any telemetry you don’t know about and assuming that all of it remains optional, you’re absolutely unaffected. However, they now have a license to everything you do within Firefox which they state they will only use to “help” you. Does training their AI model to make targeted suggestions to users count as “helping”?
On another note, taking back a promise not to sell users’ data, even if your personal data is protected because you rigorously police the about:config page, is not something many people are enthusiastic about. Just because I’m safe, doesn’t mean everybody else is.
I see your point but think it’s also valid to use Lemmy or other social media to engage only with memes or whatever else people enjoy. Absolutely, everybody should stay informed and passionate about the rapidly crumbling world, but there’s no rule that they specifically must do that via Lemmy. If someone chooses to use their social media as a haven from the real-world issues they encounter everywhere else, then unless Lemmy is their entire life, I don’t see that as a problem.