To look at the same thing in a different way:
It's fun to experience some of the texture of a particular period of time and the values therein and the ways that period differs from our own time and values.
On the other hand, the standards of the 18th century would NOT fly, even in the countries where it originated, in the world of today. And similarly, I would expect that with the progress of tech levels from perhaps 4 or 5 to 9, that this would be a general reality. The odds of people putting up with some of those standards of treatment of beings still persisting at higher tech levels and after thousands of years is ... remote... in my view.
Royalty now, even only 200-350 years from the inspiration of Traveller, feels precarious and I could see many Royals fading to much smaller roles and expenses. And that is because once ideas our out there that these sorts of autocrats are not required, then there will be movements to remove them and grant more rights to the average citizen.
Now, it may be tolerated to some extent as a useful structure to manage the overall structure of interstellar trade and defence in a snail-mail message delivery empire. But even then, likely only insofar as the individual citizens on their planets are largely left to make choices (some may choose to live in a dictatorship.... people have strange notions).
To me, this suggests the Imperial government as a trade and overall defence overlay, with some additional agencies and programs that have an Imperial component but also integrate or liaise with local agencies and programs of similar natures (in which case the Imperial layer is simply a way to pull together disparate agencies or programs attempting similar tasks on different planets so as to leverage shared knowledge and best practices).
The idiosyncrasies and 'prerogatives' of the nobles would be tolerated to extents and would mostly be in Courts or official events, otherwise the average citizens would hear little about things beyond their own world (or a few worlds in any direction). Much of the shenanigans of empire would occur in the lands of the ultra rich and not seen by most.
The times that the Imperium could be seen and much protest created would be when the Imperium asserts its power and tromps on local rights or where it makes decisions driven by egos or self-interest from the ruling class rather than good public policy. In those cases, the Imperium may face complaints, criticisms, and pressure from planets and NGOs and it may choose then to moderate whatever policy or strategy was setting the public aflame.
Tom B