You're not painting over the billboard, just blocking the light reflected off it for yourself. It does not affect others.
What if you only block your competator's ads? What if you replace them with your own? (..does Brave do this?)
What if you block all ads (yours, and your competitors), but in so doing, exploit the inertia of a consumer who is a.) already using your product, and b.) actively sheltered from exposure to the market?
ohh, i got it: just don't block ads for FAANG /s
Ad blockers having paying partnerships can be a problem, but something like Ublock Origin does not.
It also keeps a handy "cost to advertisers" metric you can view. I'm over $40,000 at this point.