One of my concerns is that DNS over HTTP(s) is really just a way to obfuscate DNS queries from the oversight of network level ad blockers like Pi Hole, AdBloka et al.
You might've noticed most of the new Internet protocols Google is championing move to pushing things through HTTPS where they cannot be intercepted and provide a guaranteed tunnel between the servers (statistically speaking, Google), and the browser (also, statistically speaking, Google). I would never go so far as to speculate why, but it does appear Google is heavily focused on this.
Of course, but my concern is that DoH makes it easier for apps (Chrome, etc) to handle their own DNS queries internally rather than relying on the device's network libraries.
MiTM intercepting HTTP(s) traffic on my Android devices is really difficult due to certificate pinning. The only way to quantify how many unexpected requests apps are making was to watch DNS traffic. If, one day, these apps just make a single DNS request to Google's DoH host then encrypt all their traffic from there onwards, I'd have no insight into what's going on in my own device.
