Adblocking out of the box would be hard given that most of mozillas ad money comes from search partners which are at root ad companies. They still advertise adblockers like ublock origin among their recommended addons and enabling adblocking is 30 seconds work and with sync it will be automatically added to firefox as soon as you sign into sync.

Ultimately this money is what has enabled Mozilla to exist at all. Brave is living on borrowed money from presumed future revenue from its cryptocurrency scheme which may or may not come to fruition.