I don't think the nation state model is the problem so much as how it was implemented, in many cases. In particular the application of "self-determination" led to groups of people scrambling for particular pieces of land and evicting others.
In other cases, the thrusting together of different groups behind crudely drawn borders in places with a tolerance for nepotism led to resource battles. But that is not the "nation state" per se which caused these problems.
It's the imposition of it as the only model, appropriate or not to the circumstances, that's the problem.
The nation-state emerged in Western Europe where populations are pretty homogenous over large areas in terms of culture, perceived ethnicity, language and religion - the basics of a nation-state. Most of the world is not at all like that, one reason being that most of the world isn't stuck out on the edge of things as Western Europe is. Particularly not the Middle East and Balkans, where scattered pockets remain from thousands of years of migrations. Empires are actually more appropriate than nation-states in such circumstances. Empires are big enough to even out local differences, can wield a big stick, and have an interest in order within their domains.
Hopefully there's something better than either that can be worked out in what was the Eastern Ottoman Empire less than a century ago. Some sort of federal system perhaps, where everybody comes together harmoniously to kick the proverbial out of Turkey.
I think that the Kurds have more going for them in terms of institutions and working towards a common goal, however, than some of the corrupt nation states around them. I hope they succeed.
They certainly do have a national identity which in many ways has been imposed on them by persecution as minorities
within nation states. The nation state model does not handle minorities well.
What, really, is a Syrian national identity? Or an Iraqi or Lebanese one? Or a Ukrainian one, for that matter? They have the nation-states without a national identity, which is entirely arse-about-face. The result is balkanisation, as in Lebanon from the get-go, or dictatorship followed by balkanisation, as in Syria and Iraq. And Libya. And Nigeria pretty damn soon.
The term "balkanisation" was, of course, coined by exasperated 19thCE Western Europeans whose own nation-states had developed organically. Some of them recognised that it would not work in the Balkans. Some in the Balkans recognised that it would work very nicely for
them.