I think they believe it's not anti-privacy, but a lesser of two evils.

Mozilla/Firefox simply can't exist without ads. Google same thing. So why would they actively contribute to their own demise by declaring war on ads?

Instead they chose a compromise that still allows ads but in a more responsible/private way. And you can still turn it off. Sure it should have been opt-in, but I think most people wouldn't use it then and we're back to the same problems.