It can definitely help since you're removing the network operator from the critical path. Large enterprises and ISPs are, not without reason, very conservative about breaking legacy clients but a browser vendor only has to worry about their own software in the release they ship DoH in (with some caveats they've addressed about internal split-view DNS, etc.) so they don't have to deal with complaints if, say, including an extra header breaks 5% of old IoT devices which haven't had an update in a decade.