Mackay's point is that you could get through the confusion relatively quickly, and showing in principle how to evaluate and fight the problem. I don't think it was meant as a final solution -- just to show that it was feasible, and approachable as a problem. Without getting into politics or ideology.

I got a quite good intuitive sense of the scales involved, and at least for me Solar clearly reveals itself as an outstanding source of energy (at say 150W/m2).