Generals/dictators are really bad at understanding and enabling complex economies to develop. Democracies are much better at facilitating the complex trade-offs between highly differentiated interest groups and skills sets required

This may be true, and I'm inclined to think that the evidence of the last few decades has supported this.  However the contemporary counterexample is China and it's adoption of the Singaporean model of capitalism.  I tend to agree with Žižek that the future of capitalism is likely to be an authoritarian one along these lines.

And then again, the political formations that prevailed during fossil fuel abundance are likely to be different to those prevailing during the era of abundance.

That's not to say that we shouldn't do our damndest to defend what remains of participatory democracy in Europe, encourage it's development in Africa, and encourage the invention more particpatory forms.  We should be under no illusions however that any of that is compatible with the present form of capitalism.