If you're going to argue that implementation difficulties make DNSSEC too much trouble I can respect the argument. To say that it doesn't solve a problem worth solving is strange.
ARP, and more generally any single-segment Ethernet network, is insecure, and it’s a problem. It’s just a very ingrained problem that’s unlikely to get fixed any time soon.
> The modern Internet was designed with the assumption that the DNS is insecure.
SPF and such may well be designed under the assumption that DNS is insecure but, under that assumption, they too are insecure.
I kind of wish there was a version of 'Against DNSSEC' that was just about that. The 'Unnecessary' and 'Architecturally Unsound' parts of that argument are so strong, the other bits end up feeling like springboards for DNSSECtarians to launch into debate.