It doesn't have those limitations on Windows or Android, so it must be an Apple requirement or limitation.

Yes and not only that, one can enable that as a safari extension and get an ad-free experience on safari too.

Apple themselves do not allow using anything other than WebKit unless you move to the EU or Japan: https://developer.apple.com/support/alternative-browser-engi...

Firefox addons target gecko, not webkit.

What Orion's doing is horribly hacky and prone to cause issues with a multitude of addons, and of course Mozilla shouldn't bow to Apple's incredibly anti-competitive behavior.

You pay apple for a phone that can act more-or-less as a general purpose computer with apps. Apple should let you install the apps you want, and that they don't do so is insulting.

The fact that the EU and Japan ruled it illegal, and Apple responded by only changing it in those two countries instead of all countries is doubly insulting.

Until recently Apple only allowed Webkit on iOS. In the EU and Japan now they allow proprietary engines but this means Mozilla needs to put in extra effort to maintain yet another branch for iOS without a very wide user base.