One risk in creating cryptosystems is that I think applies very much to these POS systems is that you create something, it gets broken, you revise it, broke, revise it broken, revise it broken, revise it each time adding more complexity... okay no breaks found. Is it now a cryptographically secure system or was it just revised until it was cryptographically secure against review?

That's very much the history of POS systems but it's even worse than that, because as the revisions went they added new conditions to the assumed security model so at the end of the day the security assumptions are very different from where they started. They might be secure but for example a function whose security definition is that whatever the function does it correct is always "secure". :P

There is one prominent POS cryptocurrency (I'll not name it because it's not relevant and naming it will just invoke vicious shills) which has a formal security proof that starts with the assumption that all participants have a network that faithfully delivers all messages without loss and in the same order. It's trivial to have a consensus system that is secure in that model because you don't even need a consensus system in that model: "first transaction out of any competing set wins" is an adequate policy, the network in that case is equivalent to a consensus system. (Maybe the system provides some useful security properties, but its security proof won't tell you anything about them)

In any case we're largely in violent agreement. I think.

While I can agree with your argument that some of the friction in these systems may have practical utility even if it doesn't meet a strong security criteria, the danger that worries me is that people don't actually have a clear mental model for what they do provide or what risks they have. This may lead them to expose themselves in ways that they wouldn't if the properties were better known, and ultimately result in losses greater than the benefits.

Or maybe not: lots of things work fine on fully centralized systems, or works fine even when their security rests on no one bothering to attack. But there is a little pedantic voice inside me that weeps at the obfuscation and misrepresentation.