It's a rather boring entry (like Iron Man 2) that shies away from the cosmic elements it involves and presents them in a way that doesn't match up well to the surrounding material(Ether is the Reality Stone and Odin's demeanor). Both it and the first Thor are among the weaker entries in the MCU. There's certainly good moments around Frigga, Loki, the Dark Elves being shown a threat, and Darcy being good in Kat Denning's delivery and a better comedic outlet than Eric Selvig, but all of it is interlaced in disappointing and dull material. It also features a rather unremarkable villain, which severely undercuts the film. It's also the film that killed Natalie Portman's involvement with the MCU until recently.
Even from the outside, it's difficult to doubt the reactions to this film when its follow-up can unceremoniously off several notable supporting and potential-held characters (and not acknowledge the existence of another) and still be seen as one of the best the entire franchise offers.