I think the main problem with science fiction today is that it's really, really difficult to write believable hard science fiction. It's relatively easy to write about the future as seen from the 1940s to 1960s (and lots of SF writers continue to do that... Bova, Niven, Pournelle, even Varley, these days), but it's really hard to write about a medium-distance future that plausibly follows from our world. The only book I've read recently that mostly managed it was Halting State, and it was set only ten years from now.

More and more, the kind of "SF" I find myself reading is stuff that doesn't even try; it's just fantasy with science fiction trappings, and while that can be briefly entertaining, it doesn't have the "something like this could really happen" of the midtwentieth SF I used to read.

Edit: awkward flow of text