A bad director? Wasn't Juno a good movie?
I don't know if he'd be my first pick to direct a comedy though, but he's no Paul Feig.
IMNSHO, one of the reasons the 2016 Ghostbusters failed was that it completely sucked as a horror movie.
One of the things the original Ghostbusters had that made it awesome was that it succeeded as both a comedy and a horror. On the horror side it had legitimate suspense and a real plot with multiple layers of conflict, coupled with great special effects and surprisingly good cinematography. The comedy works with this to give depth to the characters, create relationships, and provide mood. The 1984 film is one of the best examples of blending genres, so you don't have to love every aspect of it to find something you like.
The 2016 film, on the other hand, was pretty much just a comedy. The horror element was there by requirement, but it had no teeth. The jokes over ran all elements of the movie, including the side conflicts, the cameos, and the major climax as a dance scene. The special effects were cartoony. The bad guy was laughable. There was nothing really approaching scary or suspenseful at any point. So if the comedy doesn't connect with you, it's just an unfunny comedy and nothing else.
To that point, Ivan Reitman had a number of horror movies under his belt before he did Ghostbusters (Cannibal Girls, Shivers, Rabid) and even sci-fi (Heavy Metal, Spacehunters) in addition to his comedy work. He had range. Paul Fieg didn't, and still doesn't; he's just a comedian.
Jason Reitman, regardless of your opinion of Juno and others, is really a drama/comedy kind of guy. His only experience with horror is being a producer on Jennifers's Body, which was a pretty forgetful by-the-numbers movie. So, while I'll admit he gives me a lot more hope than Feig, my expectations aren't that high. Maybe he'll take some of his dad's experience into the movie.