> One failure that makes the internet inoperable also takes out everything that depended on it, which shouldn't be "everything".
While the current structure may not reflect this (and, to the extent it doesn't, this is a problem), a central part of the idea of the internet is that it should be structured so that a single failure would at most make a minor part of the internet unusable, and perhaps cause a two-way partition between remaining usable parts, not make "the internet" unusable in a general way.
These are localized problems, not common-mode failures. I'm talking about a problem with something that takes out a significant portion of the internet. This isn't about a simple network partition; a common-mode failure is a problem in something that is common to an entire class of devices.
A totally contrived example might be a worm that bricks routers (we've seen a few router vulnerabilities recently) and spreads with the speed of the fastest worms. Good luck finding "usable parts" of the internet when a large part of the routing capability needs to be physically replaced and reconfigured. This risk has grown in the recent past with the centralization of many services.
Is there a pre-existing network of diesel generators? Are there enough diesel generators and diesel fuel in a given city to power it? I'm guessing probably not.
While the current structure may not reflect this (and, to the extent it doesn't, this is a problem), a central part of the idea of the internet is that it should be structured so that a single failure would at most make a minor part of the internet unusable, and perhaps cause a two-way partition between remaining usable parts, not make "the internet" unusable in a general way.