I don't buy this line for one minute. The fact that these organizations are either too weak or incompetent to roll out difficult changes in no way means it can't be done. This is just the path of least resistance. Rather than design something good, we just slap a layer of crap on top of another layer of crap and call it an improvement. But dressing up a turd doesn't make it smell like roses.
The fact is that half (if not more) of the world depends on Google, Mozilla and CloudFlare. If they actually committed to breaking networks with a new standard, the vendors and network admins would have no choice but to slowly but surely roll out fixes, because the users need it. Maybe they should actually roll out a product that would update networks to fit an application's needs, like Kubernetes for SDN.
This feature is literally "Oh, we're having problems with DNS, but changing the protocol could be hard, so let's hide a new version of it inside some other protocol." They should stop screwing around and just release a Google Chrome VPN, which you just know they're going to release. AMP was just the amuse bouche.
Let's be real here, an advertising company does not care about privacy. Chrome implemented DNS over HTTPS a long time ago because it was a technical fix for a browser issue, not for privacy. Mozilla was slow to adopt but it got on the bandwagon. And let's not pretend that "hiding" a port number is a security feature, security by obscurity is a joke.