In a real astroid field, the rocks are easily a million kilometers apart. It's all mostly empty space. If they'd be closer they'd clump together and form a planet
I'm no astrophysicist, but isn't it possible that's exactly what that asteroid field was in the process of doing? After all, there were several "big ones" for the Falcon to land on. Especially if there are some big collisions happening to keep all the rocks from aggregating smoothly, couldn't there be a grace period between "cloud of space dust" and "planet" where there could be a dense field of sizeable rocks? However unlikely, surely there's some scenario where it's at least possible
Just once I'd like to see a movie mock this "asteroid field" trope. Instead of arriving in this area with huge boulders everywhere that you had to juke and swerve around, have them arrive in the asteroid field and see... nothing. Maybe one rock way off in the distance. Maybe have the ship get hit by a grain of sand.
Captain: I told you to take us to the Main Asteroid Belt!
Navigator: I did, that's where we are!
Captain: But, I thought...
Navigator: How long have you been a spaceship captain? Did you think it was some kind of quarry? Asteroid belts are mostly empty space!