It used to mean something when a revered performer such as Jeremy Irons is part of a cast.

But such is not the case in “Assassin’s Creed,” a film that suffers from Video Game Syndrome — it’s of interest only to gamers — simply because it’s based on a video game. And, as is usually the case with these movies, it’s about as exciting as watching someone play a video game.

I think you’d have to be familiar with the game — and I am not — to comprehend all of the goings-on here. I can say that Michael Fassbender stars as Callum Lynch, a killer involved in a bizarre murder. After his execution, Lynch discovers he still is in a kind of prison in Madrid. His keeper/caretaker, Dr. Sophia Rikkin (Academy-Award-winner Marion Cotillard), helps him understand what he will undergo: He is strapped into a gigantic robotic arm, and plugged into some gizmo — kind of like a video game, in fact — that calls forth his “genetic memory,” which goes back to his ancestor Aguilar, who was an assassin in the 15th century.

During his moments on the contraption, while he actually experiences what his ancestor did, he floats through the sky, becomes involved in dangerous escapes and defies gravity in ways unfamiliar even to Vin Diesel’s character in the “Fast and Furious” franchise.

Callum sort of lives through the memories of Aguilar and his group of assassins as they keep the prince of Granada safe from the Knights Templar. There’s also something about securing the safety of the apple of Eden and some kind of orb.

Jeremy Irons, also an Academy-Award-winning performer, plays Sophia’s father, who owns the facility housing Callum and some other violent people. He is connected to the ancient struggle between the assassins and the Templars.

What is this ensemble doing in this mess? I’m thinking that someone wanted a garage full of Teslas, perhaps, or college funds for multiple relatives. This can’t have looked that good in the concept stage, so I’m always surprised when a cast of this caliber ends up in a dud like this.

Likewise, I’m not sure whether this film was meant to be a kind of marketing ploy to pique the interest of non-players. Its lengthy, nonsensical expository dialogue only makes things drone on for non-players, who might be inclined to giggle at the seriousness with which the script takes itself.

I’ll stick with the simple-but-engaging Pokemon Go … That is, until some studio head decides that making a new Pokemon film out of the game is a good idea.