A Rebellion built on hope.
Why it is hard sci-fi
Soft on physics, careful about espionage. The film is built around an intelligence operation to recover the original Death Star plans from an Imperial archive on Scarif. The plot follows real spy-craft beats. Asset extraction, infiltration of a hardened facility, signal exfiltration through a planetary shield, and a relay handoff. The films one engineering thread is the deliberate-flaw subplot, which is a worked argument that the Death Star is a hardware-secured system with a backdoor.
Science inside it
No working physics. The films interesting model is the security architecture of the Death Star and the data-archive logistics on Scarif, including the satellite-dish data uplink and the planetary deflector shield as a single chokepoint. The Galen Erso subplot treats the reactor flaw as a genuine engineering decision rather than a fairy tale.