Solar energy is flow-limited, but our ability to use that flow is limited even more by the stock of material low entropy structures capable of capturing it. I think this is why Georgescu-Roegen suggested that terrestrial material low entropy, rather than solar energy, is the long run limiting factor. Joseph Blubaugh raises the point that most economists will say that resource prices will determine the proper scale. You are certainly right that this is a big issue of contention. Getting the proper relative mix of resources is one thing, getting the right total level of use is something else.
All proportions can be and remain just right, while the absolute amounts are growing too large.