How to train your Dragon is by far my favorite cartoon, i pretty much grew up with this show, both the movie and the series, so in a way it's hard for me to give a low rating, realistically my rating would be 2.5/5 stars.
What are my issues? *SPOILERS*
1- The huge time gap, thanks to humans and their advanced technology, dragons now feel like the least powerful thing in the show.
2- The two moms, I really don't like it when animators put this gay propaganda in children's cartoons, it's comforting for a few people, but not the most of us, every show there always has to be this gay couple, in children's show no less, we don't like it when this kind of stuff is involved with young children, I'm not saying it's wrong to be gay, I'm saying it's wrong to enforce it in the eyes of kids, keep it in adult shows.
3-Too emotional, these characters don't based their actions by logic, they do it by emotion, at some point the team split, not because bad decisions, or because something bad happen, no... they split because of they hated each other's personalities... yeah.. that's it..
4-Crapiest teammates, Alex and Eugene make Snotlout the most compliant person in all HTTYD, both of these kids annoy the hell of me, every single decision the leader (Tom) tries to make, both of them always, ALWAYS, are against it, Alex always throws some stupid sarcasm and Eugene, never likes his ideas, and even makes fun of him, but both get mad, when Tom decides to go alone -__-
5- The ending, i guess because of the low ratings, the show had to end quick, when shows do this, it always feels rushed, like The owl house for example, since Disney couldn't create an LGBT show that people hated, they decided to cancel the only one people actually liked, and the Nine realms was similar, but the issue was with ratings, the end feels soo rushed, that the aftermath was basically the credits, with a few pictures.
Those are all my issues, i personally think the show should have ended in the last movie, which the creators where correct to do so, they stated they just couldn't extended it anymore, however, if they where planning to do so, i think the Nine-realms wasn't the way to go, but maybe a series about Hiccup and his kids, something like "Hiccup and the last dragons"... something like that, the Nine realms just wasn't a good concept, basically replaces the vikings and dragons...