But trying to generously interpret the GP's and your comment, Interstellar was heavily promoted, and portrays itself as an accurate representation of a potential future, with correct physics and details rigorously fact checked, etc., a sub-category called "hard science ficiton." In reality there are numerous flaws in its physics, too many to count really. These aren't nits either--the most ridiculous physics-defying nonsense is in fact fundamental to the plot.
That's only the beginning of the problems. Interstellar was a terrible movie all-around, with plot holes you could fly a starship through. But it is why I think someone might say "It's not [the type of] science fiction [it claims to be]".
When we tell stories that don't ask a "What if?" but are just set in space without asking too many awkward questions about how space works, like Star Wars, that's just called Space Opera.
In Hard SF it's inevitable that some of the specifics will be wrong. For example Greg Egan's "Schild's Ladder" relies on a completely fictional set of fundamental physics theorems concerning a "graph theory" for quantum state. In the story one element of this theorem is wrong, but of course in reality the whole theory is made up. What matters, as in most of fiction, is verisimilitude, not truth, but _plausibility_. The fictional "quantum graph theory" feels like something that theoretical fundamental physics might come up with, the proposed experiment to verify it has the sort of "If we're wrong we might all die, but we aren't wrong" vibe of many real experiments like the first test explosions of a nuclear bomb or the LHC.
Sometimes a piece of fiction might seem like bad SF but it actually wasn't intended as SF at all. Ishiguro's "Never Let Me Go" is like that. It's astonishing to me that this was put forward for SF awards. If you assume that whatever has been done/ will be done with these children makes sense, and are on board with the story on that basis, finding out what's really going on is a huge disappointment. But if you go into this knowing Ishiguro has no interest whatever in medical ethics, genetics, cloning etcetera, then you can embrace it as a metaphor about mortality (We are unable to truly accept our own inevitable death, it's explained to us but it never really sinks in, even when we see others die we always believe we're special) and it works fine.
Yes, Interstellar is a mess. It's a spectacle, I'll give it that, but well, "full of sound and fury, signifying nothing". It has at least 50% more Hans Zimmer than it needed, the plot has vast holes left in it for no apparent reason, and the larger story seems a bit aimless and underwhelming considering the setting.
The "fiction" is only necessary for the stuff that doesn't exist today.
