Lemme get the positive critique in first;
The art is cute, the characters themselves are cute, and the secondary cast are pretty interesting and I love whenever they're on screen
Ok, now that this is out of the way, here's why I gave it a low rating.
You have to understand that kids learn from what they watch, especially the ones who can't quite separate fiction from reality (and even then, I've seen adults act out the way characters in movies do).
Pucca is a stalker, there's no other way to say it. If you genuinely think she's "just a girl with a crush", imagine what would happen if you switched the genders. "A guy who manipulates, follows and forcibly kisses and hugs a girl who genuinely doesn't want anything to do with him and visibly is very uncomfortable whenever he's physical with her." If you think that is creepy, but that the actual thing isn't, you got some serious double standards you should re-evaluate.
I'm disappointed that people think this is a good show for kids. The art is cute, sure, but the message it shows to kids is that it's okay to stalk your crush, as long as nobody calls you out on it, because they'll eventually fall for you (or something like that.) Yes, other shows have done this trope, but most of the time, the character ends up learning that what they're doing is bad.
Pucca doesn't learn that.