It's obviously not perfect but DNS-level ad blockers like Pihole or Adguard Home still make a dramatic difference, so all is not lost.

If Google ever decides to "close the door" on these too, all they need to do is make Chrome always use DoH instead of classic DNS.

I don't think this would fly between enterprise usage of custom DNS, captive portals, privacy protection etc

You can block DoH by blacklisting their domains (which is what ControlD and NextDNS do, by the way).

Do you mean that that Chrome would force users to use 8.8.8.8 as DNS provider? I don't think this would be acceptable or accepted.

Leaving Chrome is 1000x easier than maintaining that.