As you point out, one of the previous best reasons to use Firefox was good ad blocking support. But with the EULA change, shameless simping for Google and even ads being thrust onto the start page, Mozilla has made it clear this is not the best choice for ad haters or privacy conscious people. At the point you have to start digging through settings to find all the ad check boxes to turn off, it's just easier to use something else. That crowd has gone to Librewolf or Brave or whatever, and rightly so -- Firefox isn't the right choice anymore.