There's no such thing as a free lunch. The way to reduce ads on websites is to pay for websites. But, so far, that's proven less practical and acceptable to users than just putting up with the ads. But, ads are getting annoying and intrusive. So, if we're stuck with ads because folks won't pay, maybe it makes sense to try to make that situation better?
You are interpreting him too literally. What he meant was simply that it is obvious that Mozilla cares about income from their ads, not about the state of digital advertising.
Mozilla cares about funding itself, yes. But digital advertising is also how most of the web is funded - and Mozilla cares about that, too, because it directly impacts everything else under the Mozilla mission.
As a user, you might prefer no ads when asked - but an enormous majority of people have endorsed the ad-supported free-of-charge model on the web through their daily actions. So, practically speaking, we have to find a way to deal with it and make it better.
>What he meant was simply that it is obvious that Mozilla cares about income from their ads, not about the state of digital advertising
Yes. I do not agree with this statement. Mozilla as an organization, as a collective of individuals and as a steward of interests of hundreds of millions of Mozilla products users has diverse and complex interests in the direction of evolution of digital advertising. These interests are not limited to the immediate profits.