So maybe this is what happened. Just my theory:
- Paul Feig wanted his all man are morons subplot in there. Which can be pretty funny, look at Spy, but does not work with Ghostbusters. Especially because of the audience. Maybe Feig was the wrong director for this project, like Wes Anderson is for a historical drama or David Fincher for a comedy or J.J. Abrams for anything.
- While the main cast are good actors and funny comedians, they are not green screen actors and usually need physical feedback to make their roles funny or believable. You have to have imagination and a certain acting style to be good during green screen sequences. Either it works great like anything with Andy Serkis or terrible like the lightsaber dance or Adam Sandler in Pixels. That could also be the reason why Chris Hemsworth actually may stand out, because he did so much special effect works in the Marvel movies.
- Sony has focus tested their special effects for the Amazing Spiderman with the young audience. They wanted this bright CG style like a neon light show. But it does not work for this movie, because Ghostbusters actually had pretty grim style and again with the fans of the original movie, it will just not work.
So a lot of things came together and while some of the stuff in itself would not have that much impact, it may not work as a movie. You have talented actresses, but in a setting which they can not shine, a director with a certain style, which is not working for the movie especially a reboot of such an important franchise and a studio, which was producing this movie for the wrong audience.
I could be wrong, but I have this strange feeling. But I could also be just a Principal Skinner and maybe I am really not getting it anymore.