Thank you for the explanation. It has solidified my view that Brave's actions are unethical. The ethical problem with ads is that they are distracting, overly promote particular things over others for reasons of questionable buyer benefit (such as that the promoter has more money to spend on ads than competitiors), and subvert normal human behaviours (such as attention to colourful or moving things, familiarity and learning through repeated exposure, and so on) to channel money to someone.

Thus it is ethically justifiable to block ads on the grounds that we should come up with a monetisation model for content that is not ads. Blocking ads and then offering your own ads is not ethically justifiable in the above context (and in fact is a bit tacky). Personally opting to replace ads with different ads is also not ethically justifiable in the above context (and is a bit defeatist). It's nice that the replacement ads pay you money, but this is unrelated to the ethical argument (and obviously the advertiser comes out ahead even in this scenario, because otherwise they wouldn't run the ads).