Not much, except the fact that they'd have to run their own DoH servers, which they can certainly do. Right now the common public ones are known and can be bloc

Not much, except the fact that they'd have to run their own DoH servers, which they can certainly do. Right now the common public ones are known and can be blocked. We can block DoH endpoints now, but we 1) can't easily block arbitrary, say, AWS https endpoints that might be DoH servers, and 2) can't block endpoints if they're used for significant amounts of non-DoH traffic as well. I think Cloudflare may decide to make DoH unblockable by merging their DoH endpoints with their https endpoints. I genuinely think that Cloudflare is nefarious, else they wouldn't be trying so hard to get people accustomed to accepting less privacy as though it were a good thing.