Escoffier also predicted that one day we'd have much better thickeners than flour 
I like his recipes as a reference, but for anything like sauces, stocks, glaces etc., I think of them as historical curiosities. We have techniques now that will give better flavor and clarity with less time investment and much less waste.
I like roux in certain dishes where it's part of the local character, like gumbo.
But I wouldn't assume that there's any important difference between the flour you can get and whatever E. used. The chemistry of roux is such that you're basically clarifying the wheat starch. The butter is a cooking medium, and whatever starch you don't transform by browning gets dispersed and forms a hydrocolloid with the water. The protein separates, cooks, clumps together, and joins the scum on top. So it really doesn't matter if you're using flour that's 9% protein or 14%. If you're making a cake that's success vs. failure, but with roux none of it's going to be in your finished product.
