Blocking is far from 100% effective, but it isn't quite as futile as you suggest. A good many of these spoofed CIDs remain active for years and it's very common to get several call from the same number over the course of a few days if not minutes. Google the suspect number if you have any doubt, and if it has been reported to one of the telemarking sites, block it right away and you don't get the repeats. A pain in the neck but still worth the effort.
I admit to a little hyperbole, but only a little. I don't even bother googling the numbers anymore, just block them immediately. Then I get another half dozen calls within the hour with the same recorded message (or at least the first 2 seconds are the same) all from different numbers. Do they have blocking detection technology? It's clearly an arms race; before blocking there wasn't much spoofing. We could go back and forth for years, developing amazingly sophisticated electronic warfare... Or we could go straight to the punch. I wasn't entirely joking about the nukes, but I suppose a conventional air strike would suffice for a call centre. I've thought about finding their addresses and sending them letters containing flour, but while that might shut down a legitimate company for a few hours, these criminal enterprises care no more for their employees than their victims, so it wouldn't work. Bombs it is then.