Queen broke more ground than most people give them credit for. Although commercial success was always their primary motivation, they still avoided repetition and imitation. They weren't afraid to explore new directions. Even when they went Disco, they did it with class and originality.
One of the subjects mentioned in the film was how effective Freddie was at engaging audiences and involving them in the show, which is difficult to pull off in a stadium. Watch the Rolling Stones film "Gimme Shelter" and see the terror on Jagger's face as he loses control of the audience. Freddie even gets away with chiding a huge crowd for booing a disco tune, saying "it's just a record, people".
Another great story has Freddie putting Johnny Rotten in his place. So much for the stereotype of gay guys being wusses.