As long as the taxes are paid and there are no other major issues, the Empire truly doesn't care about the development of the planets. Gu Hang even suspects that after the Empire reconquers some worlds, it seems to intentionally maintain their original states.
I really don't know what the supreme lords of the Empire are thinking, but that's the status quo.
Heijian Star has a population of four hundred million—feudal production relations really cannot support too many people, not to mention that their industrial capacity is virtually nonexistent.
However, the relationship between this planet and the Gu Family is very good.
Those kings, when they want to confer more lords and more knights, need a tangible standard: Mecha Knight Armors.
Obviously, with Heijian Star's current state, they can't even manufacture agricultural machinery properly, let alone Mecha. The Mecha used by those conferred knights obviously rely on foreign trade.