Probably just a more visible "install" button would eliminate the need for half of native apps. I've tried doing a PWA before, and despite iPhones having all the right capabilities for it (they even support push now), users were totally confused installing a PWA in the first place.

Beyond that, in theory, very few things need to be native apps if OS-makers really wanted to embrace PWAs. WASM and all that, and equally importantly, access to more native APIs.