No, the Imperial elite has just succeeded in spreading the belief that autocracy is the only way to govern a structure the size of the Imperium. Since "everybody knows" that this is so, most people are OK with a hereditary governing elite. The few people who dispute this truth are regarded as kooks.
(And it's not like the governance of the Imperium has much effect on people's daily lives.)
Fair enough. But my primary point is that Solomani culture cannot be used as the sole reference point or determinant of future cultural and/or sociopolitical patterns in the OTU.