You kinda answered your question yourself a bit. The ending was controversial, and given the fact that the ending usually has the most impact on one's experience, it's understandable why opinions on this movie are a lot more mixed when compared to the more highly rated Kimi no na wa.
That being said, the ending is far from the only reason why some people hate this movie. Many have called this movie a Kimi no na wa rip-off. Although I disagree with that statement itself, it's true that both movies incorporate similar structures. This makes the plot kinda predictable for the most part, and there were no intriguing twists to make up for that. Tenki no ko focused a lot more on characters, and less on the plot itself. This is very much opposite to Kimi no na wa, so I won't be surprised if there are quite a few people who expected a similar experience as Kimi no na wa, and thus paid more attention to the plot and not so much to the characters (which I assume ended in disappointment in many cases).
Furthermore, Makoto Shinkai as a creator also has a fairly large group of haters. A common complaint directed at his two latest movies is that his writing is very weak, and relies a lot on the visuals and soundtrack to make his movies popular, because apparently that's enough to make people feel emotional. It's unfortunate but this opinion is not quite as unpopular as I hoped it would be.
On top of all that, ratings can also be influenced by indirect frustration. Obviously this doesn't apply to every rating of 1/10 or 2/10, but sometimes other factors that are indirectly linked to something can have an impact on how you rate that thing. For example, there are many people who hate Demon Slayer a lot more than they otherwise would, had its fans not started preaching as if Demon Slayer is the second coming of Jesus or something. I'm sure that this influenced some people into rating it as a 1/10 or a 2/10 what would otherwise be something like a 4/10. In Tenki no ko's case, Makoto Shinkai is often referred to as the "Next Miyazaki". If I was a huge Miyazaki/Ghibli fan who couldn't really see the appeal of Shinkai movies, I'd probably have a lot more hatred towards his movies as a result of his rising reputation and popularity.
Anyway I kinda went off on a bit of a ramble in that last paragraph lol. But yeah there's plenty to dislike about Tenki no ko. And of course people rate stuff in their own way. I'm an advocate of giving ratings based on how you feel about something, instead of based on how many flaws it has. So if you wanna give a 10 to something that is heavily flawed, or give a 1 to something that definitely isn't that flawed, more power to you. |