With surprise hit Guardians of the Galaxy, director James Gunn helped open up the cosmic end of the Marvel Cinematic Universe this summer. But he’s not convinced that other studios should be copying the comic giant’s game plan.

“Listen, I love big ass shared universes in movies,” Gunn wrote in a Facebook note posted on Friday. “But I’m a little worried about the numerous shared universes being planned by the studios.”

Franchises like Star Wars, The Dark Knight saga and even Transformers, he said, began as single films and only later blossomed into gigantic series thanks to fan enthusiasm and demand. As Gunn notes, the success of those franchises has led to just about every major film studio trying to start its own shared universe of movies.

Related: ‘Avengers’ to 'Ghostbusters’: A Guide to Hollywood’s New Cinematic Universes

“But these days studios are trying to grow trees without a strong seed,” he laments. “Studios are trying to grow franchises from non-existent films or middling successes. It’s like they aren’t taking audiences into account at all anymore.”

He doesn’t name names, though one might infer Warner Bros. massive, pre-planned DC Universe and Universal’s new Classic Monsters series, to name a few.

“In short, I think this new business model is flawed,” Gunn added. “I think filmmakers and studios should be prepared for the big picture, but never, ever let it get in the way of making a single great film.”

Related: James Gunn Talks ‘Guardians’ Sequel and Dancing Baby Groot

Gunn is currently developing sequels for Guardians of the Galaxy, and says he’s working hard to keep the franchise unique within the increasingly complex and interlocking Marvel Universe.

“I actually try to keep Guardians as much its own thing as possible,” Gunn told Yahoo Movies earlier this month. “There will be moments where they’ll intersect, but for the most part, it’s not about the Guardians and the Avengers teaming up. That doesn’t interest me. We don’t want to be subservient to The Avengers — I think we’re equal to the Avengers.”