“The city is flying, we’re fighting an army of robots, I’ve got a bow and arrow. None of this makes sense.”

That line of dialogue from Jeremy Renner’s Hawkeye in “Avengers: Age of Ultron” is the only sliver of self-awareness in the film’s 20-minutes-too-long runtime. A bunch of extremely cool stuff is happening and writer/director Joss Whedon doesn’t care if you want to know how or why.

Everyone’s favorite cast of superheroes from the past 10 Marvel movies is back, and the hot new existential threat this season is a powerful, sentient robot named Ultron, created by Tony Stark and voiced by James Spader.

As artificially intelligent life forms tend to do, Ultron goes haywire and decides to kill all humans, so Iron Man, Captain America, Thor and everyone else have to save the day.

Truly, nothing is more menacing than sentient Mecha-Spader.

Spader is easily the best part of “Age of Ultron.” Little inflections in his speech lend some personality to what otherwise could have been a generic, sinister robot. He has great talent, and his addition to the cast is valuable.

Otherwise, this movie goes through the motions. Our heroes engage in a handful of bombastic, thrilling action sequences, while occasionally stopping to sarcastically yap at each other, as has been the custom in the rest of the series.

That part of “Avengers: Age of Ultron” is worse than it’s ever been in this franchise. Whedon goes way too far up his own snark hole with the character dialogue.

The banter between the characters is rarely funny, and Whedon uses it to replace genuine displays of emotion most of the time. The characters don’t speak to each other as much as they bounce insults off of each other, and it’s annoying.

Whedon’s questionable writing extends (as it often has in his past work) to his treatment of female characters, as well. At one point, Stark and Thor have a conversation about how amazing their girlfriends are, though apparently neither of them were amazing enough to actually appear in the film.

The romance subplot between Mark Ruffalo and Scarlett Johannson also feels forced. It’s as if Whedon couldn’t let the one female Avenger exist without falling in love with one of the men.

The action scenes are as exciting as we’ve come to expect, but the film could have done a better job of explaining things. It’s often unclear exactly what everyone is doing and why.

 Things just sort of happen because Whedon wanted them to happen.

Still, at one point, Captain America throws a motorcycle at some soldiers, so there’s plenty to enjoy here.

It’s beginning to feel stale, but this formula still works even with some warts.