If you refuse to engage with the ad industry they just ignore you. Oh and the company that owns a large part of the world's ad industry and owns the browser that has 65% market share also pays like 90% of your bills.
I mean, what's step two of your glorious plan to charge fists raised into battle?
Firefox compromising heralds its own irrelevance.
You might believe that the advertisers get less of your data if you use Firefox.
Similarly: you might be less likely to have your house burgled if there are locks on the doors and a burglar alarm, even though people with those things still get burgled sometimes. You might be less cold outdoors in winter if you wear a parka, even though it's still cold. You might be less bored if you buy/rent/stream some interesting books, music and movies, even though having those doesn't guarantee never being bored. You might be less likely to lose your next chess game if you practice tactics and learn openings, even though you'll still lose if you play Magnus Carlsen. You might be less likely to have a heart attack or stroke if you take those antihypertensives the doctor prescribed you, even though those are still tragically things that can happen to anyone. Etc., etc., etc.
Very few things are absolute and perfect. It's usually a matter of "less" versus "more".
This latest thing gives advertisers more information about me than they would have if Firefox didn't do it. (Unless I turn it off, which in fact I have done.) It doesn't give them very much information about me. I'm pretty sure they would get much more information about me if I switched to using Chrome (e.g., because Firefox supports better adblockers).
For the avoidance of doubt, I do think Mozilla should have made more noise about what they were doing, I do think there's a repeated pattern of them putting things into Firefox that their users don't really want and hoping no one will notice[1], I do think that says something bad about how Mozilla is run, and I would be happier if the Firefox project were run by people less inclined to do such things. But none of that means that you might as well use Chrome instead of Firefox, if you happen to value the things that Firefox still does better than Chrome.
[1] Actually, I think they know perfectly well that some users will notice, and they've decided it's overall better PR to do the thing quietly, wait for people to complain, and then say "oh, whoops, we should have been more open about this, we're so sorry and will totally not do the same thing again in six months".
Shortly as Chrome implements Privacy Sandbox, both Chrome and Firefox will support the same levels of advertising tracking. For Chrome, this is a privacy upgrade of sorts, but for Firefox, this is a definite downgrade.
As Firefox converges on Chrome in this area, the privacy advantage evaporates.
Chrome forces extensions to use "Manifest v3" rather than "v2", which cripples some ad-blockers; in particular, the full version of uBlock Origin will run on Firefox but not on Chrome. (I'm not sure of the details about the v2->v3 migration; maybe that isn't universally true yet. If not, it will be soon.)
"Reduces" and "evaporates" are not the same thing. I see the case for the former, not for the latter.
It seems far more likely that the remaining 3% are the few people who care, and therefore, "pulling this shit" did not cause the current market share.
I’m willing to put up with slowness and incompatability when I feel like firefox is on my side. Now? I’m going back to Safari.
This is an area that we are stuck contending with. Legal solutions are needed here but that path is mired by complex and powerful lobbying. If Mozilla can push for a more private or more protective - even if not fully private or fully protective - then I’d like to see where it goes.