Easier to prevent censoring from the ISP, but you're now just reliant on another company's systems.
If you just want a solution for having a remote server execute DNS queries for you, you can just use any of the existing VPN protocols purely for DNS resolution, or even make a better performing version.
When you're in an area where your DNS provider is limited by the state, you won't consider it wasted. But if you're not and you do consider it wasted, don't use it. But saying it doesn't seem to provide any benefit is wrong and just telling people to use a VPN for DNS resolution is also wrong (at least until the ergonomics improve).
It's more a question why a company like Google would pay several engineers who are paid 6-digit sums to build this when they could build for the same or less much more powerful solutions.
It all depends on your threat model. Certainly DNS over HTTPS is not a panacea - but it certainly will help when your ISP is doing crazy stuff with his DNS firewall (anyone here from the UK).
The other (darker) side of the coin is that corporate tools to identify e.g. rogue IoT devices by their DNS signatures will have difficulties...
If you just want a solution for having a remote server execute DNS queries for you, you can just use any of the existing VPN protocols purely for DNS resolution, or even make a better performing version.
All that overhead HTTP adds is wasted for this.