Why wasn't this movie as successful as it could have been?
I think it over-relied on nostalgia from the original move, rather than creating a compelling story.
The mini-marshmallowmen were just corny. Kind of like the Ewoks in Return of the Jedi
None of the characters were funny or compelling. I realize that that the focus on child actors was likely inspired by the success of Stranger Things, but perhaps due to unoriginality, poor storytelling, or overuse of CGI, it just didn't draw me in.
I did like when the original Ghostbusters showed up at the end.