Capabilities are a technical problem with a technical solution. As in: an app can't use the microphone or access the Downloads folder without getting permission

Capabilities are a technical problem with a technical solution. As in: an app can't use the microphone or access the Downloads folder without getting permission from the user, by design. What you're after is a sociopolitical problem, and would take a sociopolitical solution. It simply can't be implemented in software, and it can't be implemented correctly in all cases, period: even if the app designer is a perfect angel, and only does exactly what they've pledged to with your data, the company could be bought by Evil Corp, or get hacked.