And that doesn't even touch on replay attacks.

If you have a door lock that accepts "lock", "unlock" and "report status", a MITM attacker only needs to capture the encrypted & signed "unlock" command, then replay it later.

Many workarounds were developed to mitigate this such as random values, incrementing values and timestamps, but most were found insecure. Challenge-response systems with a short validity period are one of the better systems in use, but require bi-directional communication which can make some products (ex: garage door openers) more expensive.