Do people care if fantasy creatures are realistic or not?

Because I'm writing a fantasy novel where I have included some magical humanoids that can fly, and like most fantasy creatures, it would not really be able to fly in the real world because it doesn't have the required muscle and it's too big and so on. So I'm just wondering, does it really matter if they're totally realistic, or can they just be semi-realistic without anyone noticing or caring? I have seen that nobody really cares that the hippogriffs in Harry Potter are unrealistic (I don't care either), but I just need an answer to this.