Yeah the whole “save the villlain everyone wants to see for a sequel or [insert huge crossover film here]” is a bad strategy, especially when so much of Superman’s actual rogues gallery has been underutilized. In movies, we’ve had… Lex 5 times, Zod twice, Ultraman/Bizarro (sort of), the Engineer, Nuclear Man and Richard Pryor. But yeah. Let’s save Brainiac because he’s “too big” for a Superman movie, despite the fact that 99% of the stories he’s appeared in were Superman stories in the comics and cartoons.