So why is Harry Potter good fiction but bad fantasy? Please explain this to me.
Basically because of my personal classification of fantasy. For me, when I say fantasy, I mean "high fantasy" like Lord of the Rings or Eragon. For it to be fantasy in my mind, it must have a comprehensive fantastical world and magic system. The magic system should be consistent with the world and for the most part, the author should build a world larger than just their characters.
For me, Harry Potter has most of the first, but is lacking in the magic. I personally feel that there were a few shortcuts that JK Rowling made to further the plot that hurt the authenticity of the fantasy. After consideration, I realize that these judgements are rash, but I want to stand by my standard for fantasy. There are a few specific things that make me feel this way:
Timeturners. Time travel can be really cool, but it seems like Rowling just put these in the third book to make an interesting plot twist with Harry saving himself. And then all of the remaining time turners just happen to be smashed two books later? Even Rowling agrees that time travel presented a lot of problems to the world.
Magic system. Although the magic system seems to have some laws, magic seems to come too easily and defies the laws of the natural world rather than blending with them. It doesn't seem to take any energy to cast a spell that creates a lot of energy or even copies matter. It doesn't seem to make sense, even when considering the fact that it is magic and has its own rules. It seems like there should be some sort of internal consistency with magic and physics, and it isn't shown in the books.
Using multiple wands. I was unsure of myself in this one, since it has been a while since I read the books, but in Malfoy Manor, Harry uses multiple wands to cast a Stupefy Charm against Fenrir Greyback, and the spell has increased effect. Why does no one else exploit this ability?
There are other plot holes mentioned on different sites, but my major concern is that the ramifications of the magic in the books wasn't fully considered and there seem to be too many ways to exploit the system (like guns) that were not explored or explained.
I would say that Harry Potter is good contemporary fantasy, and I understand that this is a subgenre of fantasy, but for me, they are different. I also understand that Rowling has done a lot of worldbuilding with the additional books she has written and with Pottermore. I think that part of the reason that I feel this way about the series is because of its popularity. If she had not been as wildly popular and I had read her books, I might have considered them good fantasty. It might also be because of the clarifications/ that has made after publishing that make her seem less confident about the authenticity of the world. Either way, I think that she has given us a great series. Harry Potter has a masterfully connected plot and great characters and character development. It is something that almost all can relate to and enjoy. JK Rowling has definitely given the world a great work of fiction. That is, if it even is fiction.