It’s getting hard to find ways to call “Batman v Superman: Dawn of Justice” a success. Critics hated it, and after a strong opening weekend at the box office, ticket sales cratered in the film’s second week — to the point that Warner Bros. is reportedly overhauling its production strategy and planning to release fewer films so it can ensure the movies it does release are actually, you know, good.

So what happened? Why was a movie about Batman and also Superman — who are both rad — poorly received?

I have a working theory: “Batman v Superman: Dawn of Justice” is a straightforward movie about superheroes, and I think that since the last great Batman franchise (2005-12), the appetite for straightforward superhero movies has partially evaporated. People still love superhero movies — don’t get me wrong — but I think critics and audiences want superheros in a heist movie (“Ant-Man”) or in a time-travel movie (“X-Men: Days of Future Past”) or in a high-stakes political thriller (“Captain America: The Winter Soldier”).

Here’s the five-year rolling average of the share of superhero movies since 1987 that grossed at least $10 million and had a secondary — that is, not “superhero” or “superhero origin” — genre, according to Box Office Mojo.

From 2006 to 2010, only 35 percent of superhero movies had a secondary genre. But from 2011 through 2015, 63 percent did. This appears to be somewhat a cyclical thing.

In the late 1980s and early 1990s, straightforward superhero fare was the only thing on the menu. By the late 1990s, films like “Blade” — a vampire/superhero mashup — had shown how best to do a superhero flick blended with another genre. In the early 2000s, straight-up superhero films were back — movies in the X-Men and Spider-Man franchises did great at the box office and pretty good in critical reviews. By the beginning of the next decade, though, the appetite for more spiced-up superhero-adjacent flicks had returned. I wouldn’t be surprised if at some point, the pendulum moved back in the other direction.

At the moment, though, there’s some evidence that the era of straightforward superhero movies is coming to a close. In a given year, some movies will come out that are straightforward superhero movies and some will have that secondary genre, but lately we’ve seen that the box office dollars are increasingly derived from the latter group. Here’s the three-year rolling average of the share of superhero-movie revenue that straight super flicks were responsible for:

The writing has been on the wall since “Spider-Man 3.” Don’t make superhero movies anymore. Make boxing movies or horror movies or heist movies that happen to feature superpowered people in tights.

All of this is to say that, yeah, “Batman v. Superman” kind of sucked, but it did give Warner Bros. a reason to keep making more movies based on DC comics. Next up is “Suicide Squad,” which should be a heist movie in superhero regalia, followed by “Wonder Woman,” “Justice League: Part One,” “The Flash,” “Aquaman” and more. It’s not impossible to imagine these films pulling from non-superhero genres: I’d watch the hell out of a Wonder Woman movie set in World War I France, a Shakespearean Aquaman movie or a Flash-set high school comedy. Warner Bros. needed to give the Justice League a shot in the arm, and judging by box office receipts, it did OK — not great, but OK. Now comes the hard part.