This is sort of unfortunate news to me, as I take this as a sign that they won't do adblocking by default. I think this is a mistake; users want ads to be blocked. Especially on mobile, where it's more important from a perf perspective. Brave has ads blocked, Opera has ads blocked. If Firefox wants to follow the lead and be a privacy focused company like they say, then they need to block ads.
Successful ad blocking would kill the advertisement revenue stream. This revenue stream is what pays for the content you enjoy, so ad blocking kills content. I like content, and I don't mind paying for it. I'd prefer to pay with money, not via ads. Give me that option. Further, I don't want a subscription. I want to pay as I go, at the rates ads pay. 50¢ per thousand pages sounds ok to me.
Ad-blocking is a lot like using a DVR, or a VCR. Someone sends you data and you have the right to not view all of that data. The company has the right not to send you the data if you don't pay for it, but they don't have the right to tell you that you must view all of it.