Ad blocking, not any way to run "browser extensions". The parent is saying "all you need to do is look at Chrome on Android & the fact that it does not allow extensions at all." iOS doesn't allow any browser vendor to let run extensions too, let alone run them in Safari.

This is incorrect. iOS Safari does have the ability to run extensions on a page via the "Share extensions" feature.

See detailed comment here: https://news.ycombinator.com/item?id=20050936

Safari's content blockers are third-party extensions. It's not Turing-complete code execution yes, but it's still a meaningful kind of extension compared to Chrome's complete lack of them.