I don't entirely disagree, but... I can see Olaf Stapledon from here, slapping a monkey wrench into his palm. I think he wants a word with you.
More seriously - I think your argument about difficulty can be turned on its head. If SF is full of big ugly lumps of exposition, doesn't this demonstrate that *telling* is harder to do (well) than *showing*? If a writer wants a challenge (and I agree that writers challenging themselves is a good thing), wouldn't it be a greater challenge to "tell* with as much elegance and eloquence as *showing*?
Stapledon is famous for telling, in great dry didactic chunks of it. To take a writer with a more durable reputation, and one who's probably closer to your heart - what about H.G. Wells, and "The Shaoe of Things to Come"? The presentation, after all, is very like Stapledon's "Last and First Men" - it's supposedly a history textbook, dictated from the future by unknown means. Could it usefully be rewritten as a straightforward *showing* sort of narrative? I think the result would be a much less intriguing book.
I can see your point, certainly, but I can also see Tade Thompson's, and you and he are both writers I respect. Writing advice like "show, don't tell" is up there with "don't use adverbs" or "the passive voice is to be avoided" - they're guidelines with cogent reasoning behind them, which have been elevated (or degraded) to the level of rigid and unalterable rules. I think it was C.J. Cherryh whose first rule for writing wa "no rule should be followed off a cliff", and I do think that one, at least, is sound advice.