Why is fronting these systems with a central haproxy with TLS termination or similar not an option?
Plenty of people leave these devices without encrypted connections, because they are in a "secure network", but you should never rely on such a thing.
We used to use Firefox solely for internal problem devices with IP and subnet exclusions but even that is becoming difficult.
It's not different from IPSec, GRE, VXLAN, etc. It's just the new hotness.
We use VXLAN extensively in our network, btw, and IKEv2/IPSec tunnels between sites.
Just because it can be used to recreate VPNs traditionally used to remotely dial into a secure network zone doesn't mean it shouldn't be used in far smaller use-cases. WireGuard doesn't constitute anything like a full VPN solution on its own.
Pick your poison.