One should not confuse energy-efficiency with sustainability. Yes, pushing simpler frameworks to its limits is good, but it is not the main issue, nor it is enough given the exponential growth in demand that we have been witnessing.
Can you expand on that? What's the main issue?
I tend to disagree, in the same way that it is better to use higher efficiency class dishwasher or washing machines it is better to use code that achieves the same with less computing power. Saying that the increase in energy demand through reason x does not mean that efficiency efforts are in vain.