Unfortunately I think this is going to be an inevitable problem with any software repository. F-Droid just expects users to go to the repository and inspect the code if they have concerns, or to trust the developer. Google can verify their own code isn’t malicious. They can’t audit the code of potentially millions of apps submitted to the Play Store that will inevitably ask for access to your entire filesystem, if given the option. Because let’s face it, the majority of mobile apps these days are just spyware whose primary purpose is hoovering up as much data as humanly possible to sell to data brokers.