That's like suggesting that someone using LLMs to assist coding, could save themselves the trouble by writing the code by hand.

Yes, Firefox could do everything, but then it'd turn back into Mozilla. The whole point of the extensions framework is to allow modular extensibility. And it's much easier to vet for malware than to code afresh and maintain.

What stuns me is that most people still use browsers that cannot block ads, seem genuinely annoyed by ads, but don't want to even try switching to a browser that will easily block those ads. It's amazing how much crap people are willing to wade through when the alternative is trying something new.