The nation state marshals resources for war better than non-state entities through economies of scale and the ability to command and direct central planning efforts although it suffers a concomitant lack of agility and innovation due to the necessity of creating large bureaucracies to execute the formation of large armies and still Clausewitz’ Trinitarian notions are certainly relevant today. Subject to misinterpretation by non-German speakers, his complex theory is just so because the notions are…complex. Bassford and Villacres make the best summation I have found:
Clausewitz defines the components of the trinity as (1) primordial violence, hatred, and enmity; (2) the play of chance and probability; and (3) war’s element of subordination to rational policy. 
As with so much multilingual literature in history, proper translation is key. The Trinitarian notion is much greater than the sum of its parts. The last clause is the operative measure of effectiveness in harnessing what van Creveld would call “fighting power.”
Like so much that we discover when divining the auguries in strategy and grand strategy, Clausewitz provided a solid basis from which interpretations could be rendered. The rationality of policy must be embraced through the parochial lens of the respective sides in a conflict. Risk and the assumption thereof is a major component of daring and combat calculus that when it fails may look irrational but had a rational intent to begin with.
I think that Schuurman and Echevarria are wrong in their assessment of Lind and van Creveld. The latter confreres posit generations of warfare and Echevarria especially fails to see that they are not distinct succeeding stages or a new mode of warfare but simply additional permutations outside of conventional warfare. Both Lind and Van Creveld will certainly acknowledge that irregular and non-state warfare practices are as old as mankind. The Vietnamese campaign against both the French and Americans clearly used both conventional and irregular means to fight a simultaneous war against invaders.
There is no doubt that a Trinitarian analysis can be useful in prosecuting the irregular wars and conflicts that pepper the planet but van Creveld and Lind are simply saying that additional factors are at play and bigger is not necessarily better. Echevarria is not all wrong, he makes a great point:
“It also means that one-sided, McNamaraesque formulae and facile, prescriptive theories like effects-based operations will always be around because the arrogance that underpins such thinking seeks to control the variable nature of war. Finally, it means that it is possible for war to have a changeable nature, and yet still be war.”