There’s a subset of native iOS app capabilities that's equivalent to what any unvetted web site can do today in Safari.

So why can’t we have sideloaded apps with such capabilities?

(so I’m not talking about VPNs, access to all your photos, your contacts, etc)

There would be great benefits in the user experience, because even though the functionality might be equivalent, native apps often look & feel better, are more familiar, and automatically have an icon on the home screen.