A lady named Linn Ullman wrote a book called Before You Sleep. In it, she has some magic realism, which includes a guy getting turned into a mackerel. The protagonist puts him in a bowl of water.
A reader’s response to this was that it wasn’t realistic. Because…mackerels can’t live in tap water. (They were right. Mackerels are a salt water fish).
The thing is that often readers will swallow your whoppers but notice the little things. When I met Naomi Novik at World Fantasy Con a few years back she preemptively informed her fans that yes, she is well aware that there is no way Europe could produce enough meat to feed all of those dragons.
(Sadly, we also see this phenomenon amongst people who object to, for example, black people in worlds only loosely based off of Medieval Europe. Although we know what their real objection is).
So, what can you do about this? There’s two things you can do.
Get the Small Stuff Right
When it isn’t important to your story, then make sure you follow the rules of physics. Or of what actually happened in history (which includes black people in Medieval Europe, ya know).
Do your research and try to get those little details right. I’ve personally rolled my eyes hard at, for example, a certain very famous author who thinks gelding is a breed of horse not a term for an altered male. She got everything else so right…
If you can corner experts and check things with them, do. But don’t assume readers won’t notice. Because you can guarantee that they will.
Own the Stuff that Needs to be Wrong
Sometimes, though, you need to be wrong. Andy Weir needed the windstorm on Mars even though it’s impossible for it to happen. Temeraire can’t happen without the dragons. Even the mackerel in a tap water bowl…I guess she could have picked a different fish?
If you know it’s wrong and changed it for the sake of the story, admit it. If they won’t accept that, they aren’t your readers.
Sometimes the science and the accuracy have to take a back seat to the fun and the story. Let them.
Just remember this: Readers will notice sooner or later. Really picky betas, if you can find them, are your best defense against genuine mistakes.
Things that the story needs? You just have to own them.