The animation could do a bit of work. As for the plot, it's intriguing enough, it manage to hold my attention. I think the modern ones have a lot of struggles ahead because dragons like them if they exist in the modern era they'll get hunted even more than the viking era and Kullerson and co are not influencial to change people's mind unlike with Hiccup who's father is the chief of their tribe. I'm quite curious as to why they titled it "nine realms" and how they will navigate those kind of struggles. As for characterization, each character has their own unique personalities and I think I could even see Hiccup and Astrid in Kullerson, the loyalty, their intellect and courageousness. Same for the others too, it's like watching the grandkids of the original dragon riders.
I love the lessons that you will get such as be more accepting to people who are different from you, lessons about friendships and etc.
I do believe that this has the potential to get even better.