> The advertisers get your data either way, so why not use Chrome?
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".