It would be interesting to offer a curated App store with patent indemnification and malware scanning on Android. Do the whole thing, the APIs the eco-system. Without a particular vendor lock in (like amazon fire for example) you might be able to capture the Chinese OEM market which would be a lot of devices.
Very hard road to travel though.
Speaking of app stores for Android, there’s also F-Droid¹, although admittedly, it’s not much of a 'store' considering it only lists FOSS (Free and Open Source Software).
Amazon have their own app store for Fire devices and Androids. It requires installing Amazon's apk though, which also requires changing a security setting.
Webapps...
Web does not and will never have the same quality of experience as a native application.
What is missing in your estimation?
WebAssembly and efficient arrays bounds checks.
Do you use slack? Is that a "web" app or "native"? I think the lines are blurring.
It is like using all web apps in native wrapper and the telling that all web apps looks like native apps.
Slack desktop is a webapp packed in native wrapper.
I use the Slack web app, but others heavily prefer the "native" aka "fat" client. The fat client isn't much more than a wrapper for the web, but both are more than just an interface for the API, which can be a bit laggy.