I really don’t care how realistic your work is so long as you don’t suddenly try to have it both ways.
Frex; Civil War in Marvel.
You can have spandex-clad heroes having city-block-leveling fistfights in the middle of downtown Manhattan and I will cheer and whoop. I will never question how they could have these powers, avoid killing everyone in the city, etc etc.
The moment you start having “real consequences” however, like people dying in collateral explosions and so on, my suspension of disbelief not only goes away, it violently rearranges everything I’ve seen up to this point. Like, it’s going “Okay, why did all those other times they leveled a small town not matter but this one time it’s really important?”
Don’t spend half your work building up a fantasy with certain genre handwaves (eg, space-opera style dogfighters in Spaaace!) and then expect me to suddenly take things realistically with no warning (eg “Wait, why are you bringing in relativistic physics in my space opera?! No, you’re making your dogfights look stupid retroactively!”).
The same is true of fanfiction. If the original series handwaves away certain stuff (like PTSD), then suddenly expecting us to take it super-seriously just causes the whole house of cards to collapse. You can have your magic supers ninja if you want, but start having realism come into play and I start giving the stink eye to the entire concept.