There’s a long-running argument in sci-fi circles about what qualifies for the title of “real science fiction,” vs science fantasy, space opera, or some other subgenre ghetto intended to prevent Foundation from sharing a shelf with Space Raptor Butt Invasion. But how shall we identify science fiction subgenres, or even alternate genres? The “hardness” of your science fiction, a Moh’s Scale determined by whether the dead hand of John W Campbell can scratch your manuscript with his fingernails? The “literariness,” a quality which seems to mean “allows broke graduate students to smugly assert that they have found a deeper meaning than the undergrads?”
Other than as a way of helping readers to identify books they may enjoy, who cares? Thanks to the era of self publishing on demand, sci-fi so crunchy that its hypothetical nuclear weapon draws the FBI (it really happened) can now come off the same press that moments before printed a run of My Little Pony-dinosaur intercourse body horror (hasn’t happened yet, to my knowledge, but I’ll confess to not having googled that). One need not crowd out the other, we are no longer limited by the page count of the viable magazines.
The title of “real” sci-fi is now simply an in-group identifier, meaning alternately “Campbellian” or “shares the right politics” depending on usage. Does Childhood’s End really hand wave away any less science than, say, Stargate? Is Time Enough for Love to be taken more seriously than a Warhammer 40K novelization like Eisenhorn, simply because the former mentions some real historical events while the time traveling immortal man is screwing his own mother?
The correct amount of hand-wave in a science fiction story is “whatever is needed to tell the story,” with a typical caveat of “and no more.” If you’re telling a “hero with wrench” story, you should probably keep what he’s wrenching within the realm of the plausible. Sword and Planet? Hey, go nuts, but breaking laws of physics that aren’t germane to your story is probably going to take me out of it.
As for the people who won’t take you seriously if you don’t stick to the rulebook that comes with their classification system: do you really want their respect?