What you said makes sense from a technical standpoint but not from a practical standpoint. If I’m losing good adblock on Chrome, but good ad block still works on Firefox, it would be easy for Mozilla to put up some blog posts or tweets or whatever to point out that they are a great option, because they’re adblock isn’t going anywhere.

This is an obvious concern for many users, Mozilla has the capability to issue a press release or anything at all, and they’ve chosen not to do so. Therefore, people are reasonably questioning why they’ve chosen not to do so. Free marketing but they’re throwing it away, and their best defense for doing nothing is essentially what you wrote, which is essentially to dodge the precise issue at hand.