I can kinda see what he means. This movie's climax was a balls out holy crap invasion with tons of explosions and things being destroyed. Loki seemed kinda secondary to all that.

I preferred the story Loki had in Thor because it was more tragic and personal. In Avengers he was more RAAAAAH!!! I KILL AND RULE YOU ALL!!!! ALIENS EVERYWHERE!! And in Thor he was more, "NOBODY LOVES ME!! SADNESS AND ANGER!! ;_;" And Tom Hiddleston's sad puppy dog eyes are just so endearing. It's really what sold him to me.