Of course, and it's obviously easier to configure a single recursive resolver to prefer encryption wherever possible than it is to try to configure each client

Of course, and it's obviously easier to configure a single recursive resolver to prefer encryption wherever possible than it is to try to configure each client (or in the case of DoH, each program) to do opportunistic encryption. The point is that these requests don't go to my ISP's DNS servers. And for the other people who're making up unrealistic scenarios such as the ISP trying to MITM all DNS, not just queries they answer, there are many forms of tunneling that can be used such as VPNs. It's still easier to do one solution for the whole network than individual solutions for each client (or each application, for DoH).