Reason #173 why I choose to believe The Hidden World isn't canon: we were robbed of Hiccup being a competent, respected chief.
In the books, Hiccup doesn't want to be the chief or king, but he recognises that no one else (not even his Dad) will do The Right Thing in that position. So he steps up and takes the responsibility, not because he wants it but because it's the right thing to do.
Hiccup in the shows/films also doesn't want to be chief. RTTE and HTTYD2 make it clear that Hiccup would much rather just wander. He wants to explore, to discover, to learn - but in RTTE when Stoick points out that they're stronger together and he needs to start taking more responsibility, he does the right thing (but not the thing he wants to do) and returns to Berk to learn how to be chief.
In HTTYD2, he is clearly resisting, preferring to be exploring and avoiding taking responsibility. BUT when shit hits the fan and Stoick dies, Hiccup steps into the gap. 'A chief protects his own.' He puts aside his own feelings and saves Berk, then accepts the mantle of chief when it's offered to him, despite clearly still dealing with his grief.
AND THEN. We get to THW. I know it's only been a year, but Hiccup seems to have learned NOTHING. He's still flitting around, desperate to be out exploring. He's still longing for adventure, longing to be in the sky and on the move rather than grounded in his village.
And that's his character! I love that about Hiccup! But there is something extremely powerful about a leader doing the right thing even when it's hard. THW Hiccup doesn't do this.
He takes no responsibility for the issues on Berk, like the overpopulation and overcrowding. He dismisses the issue, doesn't want to talk about it (RTTE Hiccup would never).
He lures Grimmel to his house to hear what he says rather than just stopping/capturing him.
He makes an impulsive decision to lead his people away from their home of generations. It's also selfish - HE wants to find the Hidden World, so he uproots literally their entire way to life to find it, with no regard for how anyone else would feel about this.
When they get to New Berk, no one really respects him. We see no evidence of Hiccup leading or being listened to. He has no plan beyond 'find the Hidden World'. He's not thinking about his people ('protecting his own'). He's only thinking about himself and Toothless.
Even the decision to send the dragons to the Hidden World feels like a decision a weak leader would make. RTTE/HTTYD2-Hiccup would fight for the world he wants to see. THW Hiccup just lets it slip through his fingers because it's hard.
It's maddening. Hiccup was set up to be a GOOD CHIEF. We didn't even get a Hiccup desperately trying to do the right thing and getting it wrong. All we got was a child.