This. Apple's Safari (on iOS and macOS) is the Microsoft IE of 2020s. It's unbelievably behind the more sophisticated browsers (Firefox, Chrome) and yet, Apple couldn't care less.
It's not IE by any imaginable standard. And it's only "unbelievably behind" if you count all the non-standard APIs that Chrome ships by default and calls them standard.
A browser that doesn't support extensions unless they're installed as separate apps on the platform is not worthy of the name "browser"; it's a lock-in mechanism.
As for why Safari isn't the new IE, I recommend Breaking the Web Forward https://www.quirksmode.org/blog/archives/2021/08/breaking_th...