Brave likes to push BAT (and thus its own ads replacing the existing ones on the web) but it's ultimately opt-out. Same with their analytics (which, in fairness, Firefox also does by default).
Brave doesn't replace web ads with their ads. Their ads they show you for you to earn BAT are in a totally different area. Places like system notifications.
I don't support Brave, but it is important that we criticize them accurately.
Bought a new Pixel 7 Pro and wanted to use Firefox but scrolling was just so bad, lots of stuttering. Using Brave now and am very happy with it. You have to turn off some sneaky shit initially though.
Firefox does exactly the same: they have a lot of telemetry, they push their own services (pocket/vpn), they are in bed with Google and evil companies such as Amazon... What's the difference?