"local" travel amongst systems simply requires the use of these wormholes. "non-local" travel amongst sectors requires Mass Effect-esque relays to throw you across the galaxy. The gates don't work, but the wormholes do because wormholes are natural and not man-made.
You know, I need to dig into the lore, is the situation with the gates something like EVE Online's lore of the EVE Gate? The EVE Gate linked back to the known galaxy after everything there was explored and settled. Settlers flooded the EVE galaxy until some sort of unknown event caused the gate to collapse, leaving tons of un sustainable colonies in the EVE galaxy stranded. As the colonies fell apart with only a few left with the resources to become sustainable, it took millennia before the settlers could reach a stage where they were capable of space travel again. Knowledge of the Milky Way that lay on the other side of the closed gate was lost by the time the colonies reached the timeframe that the game plays in, all the 4 Empires know is that it was what brought them to the EVE galaxy.
Is there something similar with Starsector? Was the Sector cut off by an event, leaving everyone stranded and over time the knowledge of how to use much of the technology was lost to the peoples?