Mozilla advertised Firefox Focus to block tracking and ads before. And it blocks some ads.[1] It is not possible to block tracking effectively without blocking some ads at least. They could have stopped to advertise ad blocking because people who wanted ad blocking wanted better.

[1] https://news.ycombinator.com/item?id=48557156

It was originally pitched as a "distraction blocker" and it works in two modes. As a browser and as a content blocker, if you enable it in Safari's extension settings. I've still got it set up as a content blocking Safari extension (you find that in Settings -> Apps -> Safari -> Extensions) and it still seems to be blocking ads for me. Maybe not as many as it once did, but I just turned it off to see, and that made an unpleasant difference.

I think I've been using it for 10 years (or so) now. It's my favorite thing Mozilla has done on iOS.