You make a good point - the sandbox of the browser is a genuine improvement. It's crazy to think that on some desktop OS's if you download and run a weather app, it probably has access to all the files and peripherals you do (camera, microphone, etc...). Apple is doing good work on this front with macOS as are Linux devs with Flatpak. Mobile operating systems do a good job of isolating apps too.

Windows though... seems to be stuck in the 90's.