I still think 'Nightfall' is a vastly over-rated story - certainly not Asimov's best, and yet it was voted best ever sf short story prior to the Nebulas by the SFWA.
I think I would agree with you there. I can see it being representative of sf in one respect, however: it addresses some of the main concerns of much of sf -- the balance between science/knowledge and superstition/ignorance, with all the implications of that; a worldview based on knowledge gained through exploration and rigorous application of experimentation opposed to the more authoritarian, traditional worldview inherited from the past. And, of course, the lapsarian idea prevalent in so much sf that societies rise and fall frequently....
Still, I would put it somewhere below the mid-range of Asimov's tales in quality, and don't think it deserves (or can truly support) the sort of reputation it has.
John Clute has said that every sf novel contains three dates: the date it was written, the date it is set, and the date it is about. When the first two are effectively the same but are meant to be different... then the book fails for me.
This, I'd say, ties in well with various other points you've made about the writer depicting their milieu. And, of course, if the first two are too similar, then that does show a failure of imagination in various ways. However, I'm wary of being too pedantic about this, or the mistaken/outdated scientific or technological predictions, as I think this misses the point of sf as literature. To cite an extreme case: when I was working in a bookshop here, one of our regular customers was a big fan of sf, bought a large load of sf books each week. However, he couldn't enjoy any book where the science had been superseded. It completely killed it for him, no matter what or how great the other virtues of the tale were. This seems, to me, to be pedantry verging on making oneself blind.
The same, I think, is true of some of the instances you cite, such as the bit about computers and the like. If these are major plot-points, then yes, I would say there is a right to heavily criticize the writer. If they are incidentals and not particularly important to either the plot, character development, or the concerns the writer is addressing, then it becomes a minor flaw, nothing more. This sort of thing is common in all forms of literature, and the question is whether the work has other things which compensate for this. Enough such compensating factors, of course, makes it possible for a tale to make it into truly classic status (sf or no).
As for the sexism and such... well, that is also our current bugaboo, and I'm not at all sure it is a fair criticism of sf any more than it is of any other form of imaginative literature. If it is an unconscious thing, depicting the writer's own attitudes, it may well be a fair criticism. If, on the other hand, it is consciously used for the purpose of critiquing or satirizing such ideas and practices, that is another thing. Either way it, too, is often an incidental part of the work. A flaw, but not necessarily something which overrides the other qualities it may possess.
All this having been said, however, the better a writer is at overcoming these points, the better the work is likely to be as a whole. My caution is simply to not let such flaws necessarily debar suggesting such a piece even to a new reader of sff. Again, it depends on the individual to whom you are making the suggestion; if they have read a fair amount of other types of literature, from various periods, then such things are not likely to throw them or pull them out of the experience if the story itself still resonates with some aspect of the human experience. After all, sf is, as I've said elsewhere, simply another form of mythopoesis, and the heart of any good book is how it relates to being human and what insights the writer has to give on our shared experience.
