Well, it’s not a matter apps coming from Google store, as F-droid apps may be concerned too.
I do not trust an open-source app because it’s open-source, as I will never audit the code, and build the app from that code, all by myself.
I trust a reputation, and cross fingers.
So, having the OS prompt me if I wish to allow network access for every app I install would be in the same logic than the permissions we are prompted to give access to contacts, localisation, and so on.
But OK, I understand eOS does not provide this.