There are a LOT of things you see all the time in fiction that are totally unrealistic. Not only do characters in stories typically get knocked out and remain unconscious for hours, but they then regain consciousness, shake their heads, and they're fine. In real life a concussion is not something that just goes away by shaking your head.
I develop software for a living, and I regularly gape at the unreality of how computers are depicted in TV and movies. Like when the detective gets a picture from a store security camera and tells the computer guy to zoom in on some tiny object in the distance, then casually says "can you clarify that?", the techie hits a few keys, and additional detail appears in the image out of nowhere: suddenly we can read the license number on a car that was half a mile away or whatever. Etc.
I think a writer should strive for as much accuracy as possible. Sure, this means finding out how real life works. And doing research is way more work than just making stuff up.
That said, you say this is a fantasy story. This adds a dimension. In real life, people can't fly or throw lightning bolts from their fingertips or read minds or whatever. Then the question becomes plausibility. Will the reader accept the rules of magic that you describe?
I read an article by a science fiction writer once in which he dismissed criticisms of unreality in SF, saying that he found it easier to believe that people will someday travel to other stars than to believe that Perry Mason only gets big murder cases with innocent clients.
I think the key is setting the stage. If you tell me that the wizard magically teleports the beautiful princess to his castle, I'll probably accept that as the premise of the story. But I'll assume human nature is the same. If you tell me that after the hero rescues her and they get married, that when he goes off to rescue another beautiful princess that it never occurs to his wife to be jealous or suspicious of what her husband is doing with this other woman, I'll likely find that totally implausible! If you tell me, "In this magical land there is no such thing as lying: the fairies compel everyone to always tell the truth", I'll accept that. But if you never give such an explanation, and characters tell the truth in cases where real people would surely lie to get themselves out of trouble, I won't just say, "Oh, they probably tell the truth because this is a fantasy story". You have to set it up.
In short, I'll accept almost any premise if you tell me up front that this is how the magic in this land works, or this is the amazing new technology that has been invented. But you have to establish up front. You can't just keep throwing incredible things at me with no explanation. And it has to be consistent. You can't tell me in chapter 1 that the hero gets into this problem because he was forced to tell the truth by the magic fairies, and then in chapter 2 have the villain get away with a lie with no explanation of why the magic fairies don't force him to tell the truth also.