If your threat model excludes attackers able to do MitM attacks, then why use encryption at all? The whole point of all this encryption stuff is that it prevents exactly this. And I’d say nowadays an honest assumption about IT security is not that there’s no attacker who doesn’t have access to what’s going over the wire, but that there’s an attacker who has complete access to everything that leaves anything you can directly control and check.
If someone can gain physical access to your network, you’re already fucked.
If your threat model excludes attackers able to do MitM attacks, then why use encryption at all? The whole point of all this encryption stuff is that it prevents exactly this. And I’d say nowadays an honest assumption about IT security is not that there’s no attacker who doesn’t have access to what’s going over the wire, but that there’s an attacker who has complete access to everything that leaves anything you can directly control and check.