True, but the thing with blockchains, at least some of them, is that their administration is automatic and wouldn't rely on human-led institutions to jumpstart.
Again I'm not familiar with the internet infrastructure and what legal entities administer central points of failure. Could just be that blockchains would de facto be privately centralized around this infrastructure, but not for reasons intrinsic to blockchains.
And from what I gather, a major system shock wouldn't destroy distributed ledgers like Bitcoin, but just pause them. Not to say thats what you were arguing.
If it's possible for pockets of internet to subsist beyond the collapse of a government, even beyond the collapse of large swathes of society, then blockchains could well be better than gold as stores of value.