Doesn't matter to me if he pre-dates them or not, a lame villain is a lame villain. Not having a bad guy you care about seeing the good guy beat can be a big thing in movies, especially when the overall identify of film adaptations of comic books is good vs. bad. In the MCU, it's one of the reasons why Thor: The Dark World sucked and Avengers: Age of Ultron didn't live up to expectations. It wasn't enough to make this a bad movie, partially because Shazam/Captain Marvel hasn't had remotely the sort of exposure of the top heroes, or even a lot of the second stringers for that matter. I get that they're probably saving the more interesting villains for other projects or sequels, like Black Adam, which is understandable but it doesn't make Thaddeus Sivana any less lame.