It's quite simple really the technology is what's left over of a previously Advanced civilization stories of how to use the space traveling technology are passed down via oral tradition and there are Specialists that know how to use it but they don't know how to reproduce the technology. They don't and they know how to repair it ( fortunately equipment is well-designed it doesn't need repairs and won't  for a thousand years) they just know the controls, this would explain El they could be a hunter gatherer Society and still used space travel.