I might have just been in a bad mood that day (the beggars and trinket sellers were particularly aggressive), because I didn't get a similar sense of waste from places like Karnak etc.
Yes. The Romans, in particular, were a very practical people and knew it. The Roman senator Frontinus was put in charge of the water system at Rome circa 100 CE and wrote a fascinating treatise about it. In the beginning of the book he gives a long description of each aqueduct and supporting infrastructure and exclaims:
With such an array of indispensable structures carrying so many waters, compare, if you will, the idle Pyramids or the useless, though famous, works of the Greeks!