I think the marketing team basically realized that would have made a much better movie, which is why the trailers made it appear that this was what the movie was about.

See, I think that Ghostbusters and Suicide Squad suffer from the same problems: both have a couple great characters but are hobbled by poor scripting and story. Ghostbusters got undeserved critical acclaim while Suicide Squad got undeserved critical abuse.

You are right that it is a deeply mediocre film. However, it’s not the terrible garbage fire people are making it out to be.