Real talk time.
The Dark World is, of course, at the bottom of the MCU. But I'm of the belief that there is no bad MCU film. The Dark World, Iron Man 2, Incredible Hulk are all solid movies with a number of issues.
"Bad" (or "shit" as the internet often likes to use to describe something) is Fantastic Four 2015. It's Catwoman. It's X-Men Origins: Wolverine.
The Dark World suffers from a problem that Marvel Studios seemed to be scared of for the first phase and a half: not allowing movies to be longer. Both Thor films suffered from this. Even the original Captain America, which is great, suffered from it in the third act.
The Dark World is 1h 52m and I believe that includes credits. Winter Soldier is 2h 16m. If The Dark World had a similar running time, it could help Malekith become an actual character. It could be used to give some additional context to the portals appearing on Earth. We could get a little more of the Warriors Three and Sif.
Granted, that doesn't solve everything but it fixes a big problem. Another issue is that they ruined a potentially great arc for Selvig where we get to see him deal with the guilt and PTSD from Loki's mind control. Instead, they turned him into a crazy person who ran around naked.
But it's still a solid superhero film. It has some nice art design and the assault on Asgard is great. It also ends with Frigga's funeral, which is one of the best scenes in the MCU (with an amazing score behind it).