The Internet exploded into a frenzy of fanboy rage when the teaser trailer for next year’s Batman v Superman: Dawn of Justice was leaked a few weeks back. The general feeling was that filmmaker Zack Snyder’s overstuffed superhero film looks too dark, that Snyder simply doesn’t seem to understand what’s made DC Comics’ characters so appealing for more than half a century.

On the flip side, there’s Joss Whedon. A fan favorite for his television work with Buffy the Vampire Slayer and the cult hit Firefly, he graduated into the big leagues when he wrote and directed 2012’s The Avengers, the Marvel Comics-derived, team-based superhero film that earned more than $1.5 billion in global receipts.

Naturally, it was only a matter of time before the Avengers would reassemble. Now that they’re back, in the 11th Marvel film in what appears to be a never-ending cycle of movies featuring men in tights (Avengers: Infinity War – Parts I and II are due in 2018 and ’19), sequel fatigue has begun to settle in.

Whedon has said that this movie’s production took its toll, and you can see why. He’s serving so many masters here—setting up not only the next two Avengers films (to be directed by brothers Anthony and Joe Russo), but also a third Thor film, a third Captain America picture (also helmed by the Russos), the first Black Panther movie and who knows what else.

The movie opens in medias res, with Iron Man (Robert Downey Jr.), Captain America (Chris Evans), Thor (Chris Hemsworth), The Hulk (Mark Ruffalo and a bunch of CGI), Black Widow (Scarlett Johansson, three body doubles and more CGI to hide her pregnancy) and that guy with the bow and arrow (Jeremy Renner) storming the Eastern European castle stronghold of Baron Strucker (Thomas Kretschmann), or “Hydra’s No. 1 thug,” as Cap calls him. This well-choreographed sequence highlights the Avengers’ effectiveness as a team with a show of strength that unfortunately isn’t matched by any of the action scenes that follow, which begin to suffer from the surfeit of quick-cut CGI destruction that made Snyder’s misguided Superman reboot, 2013’s Man of Steel, such a chore to sit through.

The Nazi-spawned Hydra, as was revealed in last year’s superior Captain America: The Winter Soldier, had secretly infiltrated S.H.I.E.L.D., the government agency headed by Nick Fury (Samuel L. Jackson) that assembled the Avengers to protect our planet. So I’m not quite sure who they answer to since S.H.I.E.L.D. collapsed, although Tony Stark—the man inside Iron Man—points out that Cap, aka Steve Rogers, is the group’s de facto leader.

“He’s the boss; I just design and pay for everything, make everyone look a little cooler,” says Tony, who for some reason has suited up after retiring from the superhero game at the end of 2013’s Iron Man 3. He and the anger-prone Dr. Bruce Banner—who transforms into the 8-foot-tall, green-skinned Hulk when his blood pressure rises—have been working on the artificially intelligent Ultron Program, which Tony envisions as “a suit of armor around the world” that could bring “peace in our time.”

When the Avengers recover the magic scepter belonging to Thor’s brother Loki from Strucker, the “Infinity Stone” that’s contained within it unwittingly becomes the key to the creation of Ultron’s A.I. And it’s already spawned the powers of two new characters Strucker had been secretly experimenting on, twins Pietro and Wanda Maximoff, aka Quicksilver (Aaron Taylor-Johnson) and the Scarlet Witch (Elizabeth Olsen), whose abilities are summed up by S.H.I.E.L.D. agent Maria Hill (Cobie Smulders): “He’s fast, and she’s weird.”

That’s the type of dialogue Whedon’s known for, but much of the banter he’s written for his heroes falls flat or feels forced here. And Ultron (voiced in a deliciously arch performance by James Spader), who emerges in an ever-evolving robotic body as the Avengers’ nemesis, takes on a bit of dad Tony’s ironic sensibilities, quipping to such a degree that his menace is hampered when he, say, forgets a line halfway through an intimidating monologue—just to create some levity where it’s least needed.

Nevertheless, Whedon’s second Avengers adventure still lacks much of the fun of its predecessor. But he has addressed some criticisms directed at the earlier film. Take Clint Barton, “that guy with the bow and arrow” I joked about earlier. Comic book fans will tell you his name is Hawkeye, but you’d be hard-pressed to remember that from the last movie, where Whedon effectively turned him into a mind-controlled zombie during the first half, then dangled him from a building during the second. But here, Whedon makes him the most fully-formed character in the film. He also fills in some backstory for Natasha Romanoff, aka the Black Widow, and provides her an unexpected romance with Dr. Banner/The Hulk—while giving Iron Man, Cap and Thor less to do besides hurl one-liners at one another.

But it’s Linda Cardellini, who appears as Barton’s civilian wife, Laura, who gets perhaps the best line: “You know I totally support your Avenging.”

So do we. But for how long?

Avengers: Age of Ultron **

Starring Robert Downey Jr., Chris Hemsworth, Mark Ruffalo, Chris Evans, Scarlett Johansson, Jeremy Renner, Samuel L. Jackson, Aaron Taylor-Johnson, Don Cheadle, Elizabeth Olsen, Paul Bettany, Cobie Smulders, Anthony Mackie, Hayley Atwell, Idris Elba, Stellan Skarsgård, Claudia Kim, Thomas Kretschmann, Andy Serkis, Julie Delpy, Linda Cardellini and James Spader. Written and directed by Joss Whedon. At Assembly Row, Boston Common, Fenway and in the suburbs.