Harry Potter is trash. A lot of storytelling philosophers say this, and they're all right, but most of them don't even touch on the most important reasons.
It portraits villains as goodguys. The ministry of magic, as well as every authority at Hogwarts, is horrifyingly evil and portraying them as merely overzealous or somewhat corrupt but still legitimate is like portraying Nazis as nothing more than jerks. Let's consider some of the things the ministry's done.
The ministry has no legitimate authority in the first place. It's like a typical democracy that no one consented to, except most individual wizards don't even get a vote.
The rule against underage magic outside of school. If I were a parent, I'd want to unlock my children's powers as soon as possible so that they could use them for good. I would buy them wands and teach them magic as soon as they were old enough to understand and control it. But the ministry of magic would have me thrown in jail for it without even caring whether I and my children were using our magic for good or evil.
They use imprisonment as a punishment.
Some of the things they use that punishment for aren't even close to inherently wrong. Any of the "unforgivable curses", one of which simply kills a person, another of which takes control of someone's body, and the last of which causes extreme pain. Clearly all three of these can be used for good.
The rule against telling muggles about magic. I'll talk about the logical absurdity of this below, but it's worse morally than logically, because it's disrespectful and wrong to keep such massive secrets from one's friends. Threatening someone with expulsion or imprisonment to keep those secrets? That's a whole other level of evil.
Now for some of the hogwarts-specific injustices.
The rule against being up after hours is completely arbitrary, pointless oppression. It's against the rules to see the beauty of the night sky, and no matter how many times the series shows characters rightly sneaking out and getting caught and punished, no one starts to think there's anything unjust about the rule.
The way students are grouped into houses, and honored based on the collective merits of their house. Although this one doesn't violate anyone's rights, it is still deeply perverse and destructive, and like the other injustices here, there isn't any positive argument for it.
In conclusion, every authority figure in the series - including Dumbledore - is extremely evil, and Harry should've started a rebellion against both Hogwarts and the ministry.
A seven-book series about students at a magic academy was the worst possible story in which to put the epitome of an obfuscated magic system. I detail this objection in my article on magic systems, although if you've read any criticism of Harry Potter on the internet you probably know the drill already.
- A subpoint: Rowling claims that horcruxes "split your soul into pieces"; what the hell is that even supposed to mean?
There is no reason but contrivance for the wizarding world to be a secret. It must be a lot of trouble to keep it that way, given how rich and famous any mage could become by spilling the beans and doing magic for hire. Some Harry Potter fans have made the argument that the world's muggle governments would be afraid of magic and try to exterminate it, but this argument is very weak: the wizards can enchant their castles so that they're invisible to muggles, they can unleash dragons on their enemies, they can use the imperius curse to just take control of any government and military leaders that oppose them, and most importantly, they can roll back time as much as they want.
Quidditch is the worst feat of game design I've ever seen. It's a game of soccer going parallel with a game of tag, and the only way to make the outcome of the soccer half even affect the outcome of the game is to get a whopping fifteen points above the opposing team before somebody can catch a flying ball. So basically it's a fourteen-player game where 90% of the time the outcome is determined by just two of them. Rowling also never explains what makes it take longer or shorter to catch the snitch. Some games, it's stated in the book, go on for three months, while most of them end in a few minutes. So if there's no difference in the snitch, what gives?
There's time travel in it. This is an instant disqualifier.
It's riddled with plotholes. Now it's been years since I've read the books (and longer since I've seen the movies) so I can't remember enough to defend this point much, but even my brother, a hardcore fan who has read them several times, admits that it is so.
Even the prose is terrible. Aside from being severely over-descriptive, Rowling has no idea how to handle dialog tags and frequently uses "10-year-old me"-level descriptions of emotions that combine "telling over showing" with cliched metaphors (case in point: Snape just took fifty points from Gryffindor for the lulz and she writes that "Harry's anger boiled white-hot".)
Why not instead write: "Harry's teeth clenched. He wanted more than he had in a while to punch Snape in the face. He was sick of being treated like this and being so helpless against his cruelty. But wisdom got the better of him, and he didn't let Snape see his anger."