People use DoH/DoT so that their upstream DNS lookups are not transmitted in plaintext across the open internet. You can do this and still run your own DNS server on your network. The parent commenter is asking about Pihole with DoH, which is exactly this.
Hostile firewalls that block and/or intercept DNS traffic are also a bad pattern, but people don't always control their local network these days. You can't always count on 853 being open. There are valid use cases for both.
its far easier to control your network than it is to control your devices on that network - far too many closed source devices nowadays, and it’s extremely difficult to avoid all of them
