which means opendns is a non solution and should not be used.
A DNS resolver... resolves (recursively). unbound[0] would be an example.
A proxy instead only forwards to a trusted DNS server (or servers) and may cache their responses but won't do any resolution by themselves. dnsmasq[1] would be an example.
My guess is a simple proxy is less vulnerable to UDP amplification attacks (and also vastly simpler to implement and maintain).
The drawback is you need a resolver you trust, but that might be okay if you actually do have one. E.g. some DNS server that you know is safe but is not operating in your country (you might just want to proxy it so its closer to you for lower latency).
In that sense, proxies are also resolvers. Just not recursive.