This is one reason I think ECH is probably on net a bad idea. Content filtering is a legitimate use-case for lots of users/networks, and if traffic is completely opaque to all networks, you end up needing things like root level processes or full MITM or laws requiring ID for websites instead of more privacy-preserving inspection of basic metadata (like SNI) at the network level.

You could imagine a standard for a network to signal to a client that it does not allow certain privacy features like ECH, and then clients can accept that or not. Instead I expect browsers will eventually mandate ECH, so people will have to MITM instead.