Brave does not replace publisher ads with their own.
Brave does not block first party ads. Google's search ads display. Facebook's ads display. Twitter's ads display.
Brave does block other ads by default, and as a user agent, it's reflecting the valid, ethical choices of the user not to load the untrustworthy content and scripts from these poorly-coded, user-hostile third party ad networks.
If a user opts-in to Brave's ad ecosystem, then they've also made a decision about what content funding model they want to support.
There are many browsers out there, but till now there's really only been one privacy-invading ad model.
Now we have not just another browser, but another ad model which respects privacy, and after all we've learned about the current ad-tech ecosystem I'd prioritise user agency over all other considerations.
If the primacy of user agency begins to take hold, then the market will adapt and survive and even thrive within this new model.