Look, as a middle aged guy who remembers see the original movies in the theater as a kid, I loved the story/ending of the movie. I was not a hater of the 2016 version of the movie - I enjoyed it for what it was. But Afterlife was far and away the best sequel to the 1984 original. I would love to see another movie with the younger actors. However, if that is the last Ghostbusters movie we get, it was the perfect ending. As for the CGI Egon, it was done respectfully. They got permission from his family, were very tasteful with the CGI, and did NOT try to dub in/ replace his voice. He was a silent specter who was just trying to hang on long enough to protect his family and friends. When he "said" goodbye to everyone at the end, both my wife and I teared up.
P.S. I also love that it was a play on the Ghostbusters III script(s) from the early 2010s where Venkman died at the beginning of the movie (since Murray wanted nothing to do with the franchise anymore) and only appeared at the end to help save the day.