How important is it really to this story? The First Order is trying to take over the galaxy, the Resistance is trying to stop it. Is a lot more information than that really important to the stories of these new characters? The logistics of the New Republic are no more important to Rey’s story than they are to the Mandalorian’s.
When one of the main characters of the story is the ruler of the galaxy, you should expect to have at least some explanation of how the system works. It’s fine to not explain anything for a small-scale TV show like The Mandalorian, but the sequels have events that happen on a galactic scale, so the movies should at least give us some broad idea as to the political situation.