I think it's a bit of a stretch to be saying that Sci-fi writers were making accurate predictions of what would happen in the future and when. Heinlein doesn't write about space because he thought it would happen at a particular time, it's because it opened doors into interesting stories and new ways of thinking about things whilst relating back to what already exists. It's less about what is going to happen and more about what's interesting. Personally I think even today we struggle to write good stories with that cope with the existence of instant access to every other person on the planet and every fact known to man.
Sure, some sci-fi writers were openly disdainful about sci-fi as prophecy. Ursula Le Guin's famous "prediction is... not the business of novelists. A novelist's business is lying" foreword to The Left Hand of Darkness springs to mind. But some of them took their technology more seriously than others, and sometimes authors finding it easier to imagine a world a couple of decades away with space battles than one with ubiquitous mobile communication devices says things about their thought processes and the world they lived in beyond them simply needing characters to be uncontactable for the next event to happen.
And also, sometimes they were far more right about the details they threw in to be vaguely believable and less on the money about what they really cared about, like HG Wells' plot device for a world in which war was impossible which is believed to have been what inspired Szilard to create an actual atomic bomb (whilst the thrust of the book failed to convince enough of the right people of the merits of a World State). And Solution Unsatisfactory is uncannily closer still...
Heinlein has a preface to one of this story collections where he claims to not be making predictions about specific dates, but rather is aiming to put many of his stories on a shared timeline for the coherence of his imagined future.
That said, he was also obsessed with 'hard' science fiction and attempting to create plausible technological what-if scenarios.
So many of Connie Willis' books over time have had a healthy dose of running around missed connections. With the exception of her WWII period books, a young reader would pick up one of those books today and wonder why the protagonist couldn't just text whoever she was looking for.
