[Reinmar]

I'm not sure how long they can keep doing so. At what point it may affect iOS's reception in general?

From my own experience, making the app I'm working on (CKEditor 5 - a web based rich-text editor) compatible with mobile Safari is right now impossible. None of the RTEs work well in mobile Safari because of its quirks and bugs.

If Apple will overdo this (just like Microsoft did with IE6), that may affect iOS's usefulness. Sure, right now you can't build a business without your presence there, but there may be a breaking point. It's hard to imagine and I kinda doubt it will happen (I rather agree with the author of this article that Apple will invest enough to keep Safari alive), but it's a possibility. Microsoft screwed it up once, so can Apple.

[wvenable]

If you care about iOS, you don't build a web application you build a native one (perhaps using web technologies). This ultimately benefits users and Apple so there is no incentive to improve this.

[pxtail]

Probably they are doing it on purpose, cripling web-based apps/PWA experience forces user to install app from AppStore.