The Saga Will End.
Why it is hard sci-fi
Soft. The films explicit retcon of the Holdo manoeuvre, by reintroducing the Death Star-class superlaser as something a Star Destroyer can carry, is the saga at its softest. The films one piece of working worldbuilding is the planet Exegol, which is presented as a hidden world reachable only by a paired wayfinder, which is a coherent astrogation premise.
Science inside it
No working physics. The wayfinder pairing is the films one piece of consistent worldbuilding, since it is treated as a hardware key for a route that is otherwise unnavigable. The Final Order fleet is presented as planetside, which limits its launch logistics and gives the third act its narrow time window.