Yes that's true. I guess I did not mean HD in the modern sense of the word. The old analogue film contained all the information necessary, yet even at the digital resolution used they really failed my expectations. Hopefully in future digital capturing techniques will improve. Many other old films have been captured with so much more detail and resolution than the SW original trilogy though.
The new trilogy I, II, III, also seem to suffer from the same problem in my opinion. As soon as you zoom in the picture quality goes.