Thanos (Josh Brolin) in a scene from “Avengers: Infinity War.” (Marvel Studios/Walt Disney)
Opinion writer

This piece discusses the plot of “Avengers: Infinity War” in broad terms, not specific ones. For example, I mention which characters are teamed up, and which have the most satisfying storylines, but not what those teams get up to or what those storylines consist of. If you have more specific questions about whether it’s safe to read on, email me.

We’re living through a great convergence in popular culture. Disney is gobbling up other entertainment companies, having added Marvel, Lucasfilm and Pixar to its list of acquisitions. Netflix is taking on new debt in the hopes of becoming the Internet’s premier streaming destination. Expanded universes are the hottest thing going, even if that means slapping one together for the sake of appearances and marketing. And, most importantly, movies and television are acquiring some of each others’ characteristics.

The biggest compliment you can give a TV show these days is that it’s cinematic. Basic and cable premium networks are thinking more and more about cinematography, extended episodes and content that pushes the line on what they feel comfortable airing. Some expanded universes in film, on the flip side, are functioning much more like serialized dramas, weaving interconnected stories on the hunch that brand pre-awareness and an eagerness to see what happens next will keep fans coming back.

No franchise has been more committed to that idea, or more successful at executing it, than the Marvel Cinematic Universe. And although there are a number of Marvel television shows, including streaming series such as “Jessica Jones,” “Luke Cage,” ABC’s “Agents of S.H.I.E.L.D.” and FX’s marvelously trippy “Legion,” the biggest TV show of all may be the Marvel movies themselves. “Avengers: Infinity War,” which arrives in theaters on Thursday, is Marvel’s first attempt at a season finale. And the results suggest that it hasn’t quite cracked the equation on how to make great television.

A useful comparison for these purposes is a season finale of “Game of Thrones.” Both the HBO series and “Avengers: Infinity War” must check in with a sprawling cast of characters while also moving a narrative forward and providing a final image that will leave us ravenous for what comes next, no matter how long we have to wait.

When it comes to the first task, “Avengers: Infinity War” has some troubles rooted in both the size of its cast and what you might call the number of its episodes. “Game of Thrones” starts each episode with a map so viewers know which destinations they’ll be seeing; by the season finale, the characters who need to be in the same place are generally already there. “Avengers: Infinity War,” by contrast, has to spend a fair amount of time grouping its various bands together, and then it flings them almost immediately into separate fights. With one major exception, and until its final moments, it’s more a series of interconnected action scenes than an actual movie.

It doesn’t help that some of these fresh team-ups work better than others. Pairing Thor (Chris Hemsworth) with Rocket Raccoon (Bradley Cooper) and Groot (Vin Diesel) results in one joke, but not much insight. In theory, putting together T’Challa (Chadwick Boseman) and Steve Rogers (Chris Evans) should be an opportunity to follow up on some of the tensions between them that resulted from “Captain America: Civil War,” and to play with the winning sincerity at the heart of each man’s character. But there’s just no time to chat when Wakanda is under attack. On the other hand, seeing Tony Stark (Robert Downey Jr.) and Dr. Strange (Benedict Cumberbatch) snipe at each other and team up uneasily is a genuine pleasure: Those two big egos make for some seriously sparky friction.

In all these cases, it would be nice if the new pairings simply had more time to breathe. But if it’s challenging to add another episode to a series like “Game of Thrones,” which has an official budget for its final season of $15 million per hour, it’s even harder to add another blockbuster to the schedule, especially when the production budget alone for “Avengers: Infinity War” is rumored to be in the $300 million range.

As for narrative advancement, nestled — or perhaps I should say wedged — within “Avengers: Infinity War” is the outline of a genuinely interesting movie about Thanos (Josh Brolin), the movie’s Big Bad death cultist and possessor of one of the silliest looking chins to be produced in the era of computer-generated imagery. This element of “Avengers: Infinity War” is so much more engaging than the rest of the movie that it highlights a problem with the pacing of the Marvel Cinematic Universe. I wish we’d had the opportunity to meet Thanos in something more substantial than a credits sequence before this, and to get a sense of him other than through conversations between Gamora (Zoe Saldana) and Nebula (Karen Gillan), his adopted and much-abused daughters. Insomuch as “Avengers: Infinity War” gives a satisfying narrative arc to any characters, it’s to these two women, Gamora in particular.

The final image, or set of images, is the one place “Avengers: Infinity War” hits the mark that “Game of Thrones” and other series have set for it. Marvel has long benefited from its deep, outstanding casting, and directors Anthony Russo and Joe Russo make fabulous use of the hugely expressive faces at their disposal in the movie’s final, genuinely moving moments.

The Marvel Cinematic Universe may have a long way to go to match the best of what’s happening on American television, and it’ll have to work around the constraints of its scale and business model to do so. But then, it’s become a bit of a truism that the best TV shows really find themselves in their second seasons. If nothing else, “Avengers: Infinity War” succeeded in making me curious to see what comes next.