It is always soft of amusing to watch companies make all kinds of unforced errors with their products because the managers feel that they know much better than the users of the product what should be important to users. They fail all the time just to have someone else come in and say "Oh, those people, they were just holding the instructions wrong" and go repeating the same mistake.

So far in this ( software + hardware space ) there has been exactly one company that nailed it. The company is called Apple and the product is called iPhone. Since that point on Apple has not introduced anything that was not a direct play on "Our users want X, we are going to give them X, maybe with a bit of a twist"

The users are telling you that the USP of Firefox is ad blocking. If your PM says it is something else, you should replace the PM. That should be your singular focus. Everything else is secondary.