[chenmike]

This is a strange way to phrase the question. Sites that had to shift to app-like experiences are hard to find, because nowadays pretty much every web app is an app-like experience from the beginning and is created with a JS framework. The shift happened years ago.

Barring informational sites like blogs and news publications, it’s actually more challenging to come up with new web products that are NOT app-like in nature, and that do not use any kind of JS framework. Craigslist may be one of the few big ones and even it is losing market share to FB marketplace, which is an app-like experience.

[michaelt]

Depends how you define 'app-like experience'

If I start with 1990s ebay, does it become app-like when I add the ability to zoom images without a pageload? When I add a WYSIWYG listing editor? When I let people drag and drop images into their listings? When I add JS infinite scrolling to search results? When I add AJAX search autocomplete?

Or do I have to go as far as Google Docs, re-implementing copy/paste functions, taking over the mouse wheel, and adding my own text highlighting and zoom implementations?

[brigandish]

My personal "line" is when links won't work without js and urls aren't written in the location bar. It makes a site quite useless without js. I know that progressive enhancement is supposed to be a thing but I've yet to see it outside of tutorials (browsers not properly supporting PWAs could be part of that, but I doubt it).