Reality is a motherfucker. Let's just sit with that, come to terms with it. People can be selfish and petty and outright mean. They can also be kind and generous and giving. All in the perspective. Birdman is all about perspective.
Michael Keaton stars as an actor known for playing a costumed hero attempting to be seen as more than that. To that end, he's directing and starring in an adaptation of a Raymond Carver play on Broadway. No one seems to care or take him seriously, from his daughter to the asshole famous actor trying to take control of the production. When he also begins to insert alternate realities on the proceedings, shit gets wacky.
There's a scene where Keaton and his manager are going over actors to hire in the play. One of them mentions Jeremy Renner, that real good kid from the Hurt Locker. The manager says Renner's an Avenger and Keaton responds, "They put a cape on him, too?" That's the point of this movie in a nutshell, the existential horror of commodifying talent and creativity into genre and exploitation. That a scene comes later with actual explosions and effects along with commentary from Keaton staring right at the camera blasting the audience for all the dumb shit they chew and grind and choke down with barrels of laughter and… It's a rage against the machine, to quote the 1990s.
This whole movie felt like a writer/director of 1970s character pieces making a well intentioned and angry rebuke of the Hollywood system. Had Keaton and the cast not made the experience rich with character and heart, it might have fallen flat.
Oh, and I guess I should comment on the "one-shot" style of directing. It was cool, made you get in there with Keaton. I got nothing more to say.