Hurry not, Apple did the very same thing last year: https://9to5mac.com/2017/07/15/apple-reportedly-shifts-app-s...
(Submitted title was 'Amazon follows Google and bans system-wide ad blockers on their AppStore'.)
Does iOS support custom browsers like Firefox running their own engine and extension systems? They never did when I was a user.
Actually, they only work in the specific case of SFSafariViewController. This isn't available for any old webview to implement.
Safari's ad blocking is piss poor compared to it, because it is technologically limited.