Ok let me go over for a secondThe rules that are there are mostly fine if not over simplified. The list I gave are things that I believe are necessary but are not there. The rules in SJ are very minimum effort, both in what is present and the rules themselves.
Ship and hazard Detection / Tracking rules: There is an item for tracking, but for the most part spelljammer has never really had this, ship slows down when close to a large enough object.
Chase rules: There is chase stuff in the dmg.
Navigation rules: What Nav rules?
Wildspace Hazards: We have several.
Ship building: This is not even in the normal game, beyond bring in other weapons on a ship.