Question reality. You can go there even though it doesn't exist.
Why it is hard sci-fi
A computer scientist runs a simulation of 1937 Los Angeles. He discovers, mid-investigation, that he is in a simulation himself. The film commits to the layered-simulation idea and treats it as an engineering problem with users, hardware, and a logout protocol. The scenes inside the simulation hold to period accuracy, and the scenes outside hold to a near-future LA with consistent infrastructure.
Science inside it
Discrete simulation hosting, user identity migration into a guest body, and the procedural shape of a multi-user immersive system with administrators. The films best joke is that the protagonists outer reality is itself a 1990s simulation, which is hinted by a long drive into a horizon that is being rendered ahead of him.