It's because Apple does not allow Firefox to install an actual browser on iOS. Firefox on iOS is just a skinned version of WebKit/Safari. See 2.5.6:
https://developer.apple.com/app-store/review/guidelines/#per...
https://developer.apple.com/app-store/review/guidelines/#per...
So are Chrome, Brave, and Edge. And yet, they support ad-blocking extensions (and so does Safari).
They could also launch an alternative browser engine for iOS and iPadOS in the EU.
That's incorrect, and Firefox doesn't blame Apple for this. Many 3rd-party iOS browsers do ad blocking natively and/or via extensions. https://orionbrowser.com/platforms/ios