here that "empires," by which I meant the interstellar empires of much sf, seemed implausible and unimaginative. Sean Brooks replied that empires have arisen frequently in the past so they might again in future and that they might be federations rather than monarchies.
It is the monarchical form with an Emperor that I consider least likely. If such a form were ever to be adopted, as by Poul Anderson's Manuel Argos or by Jerry Pournelle's Leonidas I, then it would not occur spontaneously but would have to be a conscious piece of social engineering. Someone would have to think, as Argos does, "This archaism suits current conditions and will work better than any alternative."
Larry Niven's Known Space future history avoids a human interstellar empire but presents a kzinti one. But military conquest makes sense for kzinti.
Three questions about any futuristic sf:
Is it enjoyable to read?
Is it a plausible future?
Does it combine the plausible with the fantastic?
With much of the sf discussed here, I think that the answers are yes, no and yes, respectively.