I have no idea why people enjoyed this movie. I have never been a very big appreciator of these Miyazaki stamped films, although I don't necessarily dislike them all, but this film is the worst of them I've seen. Lets go through the details.
The animation is in constant conflict. While the backgrounds have some fairly impressive detail, the moving parts of the animation are inconsistent and often poorly done and all movement is extremely choppy. The backgrounds and characters also don't seem to work very well together in some situations as if they exist on different layers. Another example of this disconnect between background and the moving pieces is Scooby Doo, where it seems as if they locked the animators for the characters and those for the background in different rooms and never showed each other the other's work.
The sound is downright annoying some of the time. I dislike the use of Take Me Home Country Roads as essentially the theme song of the movie and each time characters sang in the movie it proved more annoying than impactful in any way, and the rewrites the main character made were pretty terrible. Also this film takes one from many other Japanese films and employs the "roaring ambiance," the obnoxious cicada and other such random noises. Aside from that the miscellaneous background music is not noteworthy, although sometimes not very very well selected, and the voice actors are generally fine.
Finally, the story and characters have basically nothing going for them. The characters are generally not believable and flat, the randomness of dialogue is off-putting, the story is slow and boring.
First off, the "romantic element" of this movie feels artificial and forced. The initial romantic triangle doesn't make any sense because we don't even know the character's relationships with each other in the first place. When the female lead says she was friends forever with the dude, I didn't even know they talked. It's also extremely awkward and all the characters fill stereotypical roles, the shy girl, the mediator (main character) and the idiot guy.
As for the main romance of the movie, the proposal at the end was extremely annoying and I couldn't take it seriously at all. Checking out books to get someone's attention is the absolute dumbest thing I've heard, the most hilarious line of the movie being Shizuku wondering if he was handsome just seeing his name in the books.
Oh it's also a great romance when the girl doesn't even know who the guy is and he just inexplicably likes her.
So yes, in the end, all of these elements mix together to form a sub-par community "classic" that I wouldn't recommend to anyone.