The Empire Falls....
Why it is hard sci-fi
Soft. The films rebuilt Death Star repeats the original engineering problem at greater scale and skips the heat-dissipation question. The shield generator on Endor is a working containment idea but the film does not engage with the energetics. The space battle is staged for spectacle rather than ballistics.
Science inside it
Shielding as a binary protective field rather than a working mechanism, fleet-scale combat coordination, and a forest moon ecology dominated by a single intelligent species. The Ewoks are the films one piece of soft xenobiology and the film commits to them as the local fauna without further explanation.