Millions of dollars in promotion and marketing won’t convince people to buy something they don’t want. That pretty much explains the box office implosion of “Teenage Mutant Ninja Turtles: Out of the Shadows.”

Like most people my age, I grew up with the original “Ninja Turtles” cartoon series and spent many elementary school days pretending to fight Shredder on the playground.

I’ve retained my enthusiasm for the characters thanks to the older-skewing comic book source material, and, more recently, an ongoing comic series from IDW Publishing which blends many iterations of the franchise into a thoughtful and compelling serial. I know words like “thoughtful” and “compelling” sound ridiculous in regard to Ninja Turtles, but it’s true.

There’s a difference between the devoted fans of a certain property and the people who feel nostalgic about the things they liked as kids. While lots of people my age loved the old cartoon, very few have much interest in what the Ninja Turtles are to a modern audience, especially to kids. Really, why would they? I only know because I like the franchise more than a normal 32-year-old probably should.

Nickelodeon currently airs a Ninja Turtles CGI cartoon series geared to kids. The show runs outside the continuity of the live-action “Out of the Shadows” and its 2014 predecessor, to the extent that the movie Turtles barely resemble the ones seen on TV.

Point being, the makers of “Out of the Shadows” don’t care about making a Turtles movie for the kids watching the TV show. The 2014 movie and its sequel are PG-13-rated movies with the superficial appearance of grittiness. They aim for an audience beyond kids and hardcore fans — one comprised of nostalgia freaks, action movie buffs, and teenagers itching for a glimpse of Megan Fox’s midriff.

With such a broad target, it was hardly surprising to see the 2014 film fall on its face in regard to story, character and overall cinematic quality. The movie grossed almost $500 million worldwide, but good luck finding anyone who would admit to liking it.

Producer Michael Bay (ugh) and his team at least recognized the awfulness of their own product, and “Out of the Shadows” does have a better grasp of the characters and what audiences might enjoy from a movie about mutant reptiles fighting crime in New York City. The movie is goofy fun in a few stretches, and “fun” was never a word mentioned in any review of the first movie.

So why did “Out of the Shadows” open to roughly half the box office of the 2014 film? I think much of the failure can be linked to Hollywood’s obsession with “fan service,” or the idea you can satisfy audiences simply by referencing things they liked in previous incarnations.

Bay and his team “listened” to fans of the Turtles, they claim, when they decided to add four core franchise characters to the new movie — mutant sidekicks Bebop and Rocksteady, the evil alien brain, Krang, and hockey-obsessed vigilante, Casey Jones.

With Casey Jones, the filmmakers went the Megan Fox route and hired eye-candy with questionable acting ability. But the other three are characters integral to the original cartoon. Casual fans, especially those nostalgic about their playground adventures, hold a special place for Bebop, Rocksteady and Krang in their ’90s obsessed hearts.

Now, all three characters were already reintroduced in the current comic series and Nick TV show prior to their inclusion in “Out of the Shadows,” but the movie most definitely models the characters based on their old cartoon incarnations. Problem is, they exist on the big screen in the most superficial way possible. Where the comic and TV series made efforts to develop and modernize the characters to fit their stories, the movie drops them into the action as vaguely defined tributes to the old cartoon.

Nostalgia is a nice feeling, and I think we all reflect on things we loved as kids with a certain level of non-critical fuzziness. But it’s best to let those memories exist without new influence. The original “Ninja Turtles’ cartoon is, I promise, way worse than you remember it.

Even though nostalgia seems like an easy sell, audiences often react poorly to “fan service” because the filmmakers don’t make the effort to reinvent those things to fit within a modern context. The old cartoon versions of Bebop and Rocksteady can’t work in 2016 without some changes. The movie makes no attempt to modernize them.

If you start with that core disconnect, it isn’t difficult to see why “Out of the Shadows” stumbled at the box office. The nostalgic (casual) fans were already burned by the awfulness of the 2014 movie, and no amount of mutant warthog mayhem is going to hide the fact the sequel retains the stuff people hated about the first movie (cast, character design, lousy storytelling).

Additionally, the marketing for “Out of the Shadows” pushed much harder for a younger demographic, as if the studio knew many adult fans felt too burned by the last movie. The trailers highlighted cartoonish antics and downplayed the action and “grittiness” so apparent in the marketing for the prior film.

But even when you market “Out of the Shadows” for kids, the movie still plays like a fuzzy nostalgia trip, and it doesn’t present the Turtles in the way kids see them every week on Nickelodeon. If kids can stay home and watch the Turtles fight better versions of Krang, Bebop and Rocksteady, why nag a parent to drive them to the theater?

All this analysis may be futile, as the success of Ninja Turtles depends on many factors beyond domestic box office, notably toy and merchandise revenue. Even if Viacom (the parent company of all things Turtles) nets some form of profit on “Out of the Shadows,” studios need to stop relying on haphazard fan service to anchor their blockbusters, because it alienates the people who genuinely love the characters. Ask a “Star Trek” fan how they feel about Khan in “Star Trek Into Darkness.”

Giant properties like Batman or Superman will endure bad movies. Other properties, like Ninja Turtles and maybe even “Star Trek” can be tainted by a bad product for a generation. General audiences are getting smarter about avoiding insincere cash grabs, and you’ve got a whole generation of Twitter-savvy oversharers ready to trash a movie the second they step out of the theater.

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Tyler Wilson can be reached at twilson@cdapress.com.