he's not an actor and it's based on a 30 minute game

...neither of which are true? He's as much an actor as anyone else in the industry, he just doesn't have a giant distributor behind him. He's a member of SAG-AFTRA, this was a union movie. You might not like how he performs, but that doesn't make him not an actor. And since you haven't seen the movie, your opinion is moot on that point.

And the game is definitely longer than 30 minutes. It's eldritch/cosmic horror, so definitely not everyone's genre, but Mark and David did an astounding job bringing it to the big screen.