The other unfair side of that is that when they say "we've all been there," it turns out to mean that people who haven't been there don't quite count as readers. We're told that fighting on a large-scale battlefield is universal but giving birth isn't, but a lot more people have given birth than taken part in trench warfare. I'm expected to care about the personal lives of certain strangers mostly because they're rich; most of us aren't rich, and even most rich people haven't been on reality television.

So, whose disbelief/skepticism matters here? If you're worried about getting past slush readers, the slush reader for a speculative fiction story is likely to have read a lot of speculative fiction, just as the person deciding whether to publish romance stories or mystery novels probably knows those genres. At some point, it may be worth saying "there are hundreds of millions of readers, I can't possibly interest all of them, who do I want to write for?" and look for ways to find that audience.