You've started using a pi-hole, and presumably are getting value from it. These protocols can potentially make it so you can't use that pi-hole at all.
Traffic that is local to a network being unencrypted is not a huge privacy problem. If this protocol was adopted by local resolvers, your pi-hole or network router could use it for any requests it makes while still preserving its ability to filter the traffic. It's basically all win under this scenario.
The problem comes back to applications implementing this in ways that can't be managed taking the option away from end users and administrators. Without the protocols specifying control and fall-back behaviours on networks that don't need or want this, it's more harmful than useful.
