Let’s be fair, star and co-writer of the original, literally died early, in protracted attempts to make a third film, with a difficult relationship with one of the other stars (thankfully repaired before his passing) so making the film deal with that in relation to the in-universe character is going to be mournful and sentimental. The fact it literally deals with life after death as it’s core premise, makes it almost inevitable. The alternative is ‘hey yeah, Egons working on the LHC in Switzerland, dream job, but y’know couldn’t come help with world changing events and be with his friends and collegaues’ and tell a different story. It’s like Ghostbusters II having to deal with the elephant in the room that is Dana and Peter, breaking up, so they can build a real relationship in the second. Because the film is heavily about people growing older, moving on, and trying to keep positive in that. It might not be the greatest sequel, but, everyone is not in the same place they were as it begins, and have changed even more by the end. Despite being accused of being a rehash of the original, it’s really completely different on a character level.