Just like https certificate authorities, the only way to fight all the AI slop will be "trusted" camera firmware that signs every image with a full chain of trust that the output was a real physical video taken will a real device at a real location.
Who talks about average people? The whole trust and cert system is only needed to guard against criminal actors or other people/organization's with ill intend. And such people are not average at all.
Embeding identity is problematic too, identity theft and stolen certificates are not that uncommon.
This would create a whole new class of attacks.