Never tell him the odds.
Why it is hard sci-fi
Soft. The films one working idea is the Kessel Run as a navigation problem, where the route is a question of how close you are willing to fly to a black-hole maw to shorten the trip. The film treats the run as a genuine astrogation calculation with a measurable parsec count, which is the closest the saga has come to acknowledging the original line as a distance metric. The rest of the film is a heist with hyperdrive.
Science inside it
Astrogation through a hazardous region of space, with the parsec count as a real shortest-path measure rather than a unit of time. The Kessel Run is the films one attempt to retroactively make sense of an off-hand line from 1977 and it succeeds.