It’s possible that whatever opportunity was offered in Ghostbusters: Afterlife just wasn’t substantial enough to make it worthwhile for him.
Moranis had previously given that explanation for the reason he didn’t appear in the 2016 franchise reboot directed by Paul Feig.
Rick Moranis will be returning to the screen soon in the forthcoming reboot of the Honey, I Shrunk the Kids franchise, titled Shrunk!, and he also appeared in an episode of the Disney+ series Prop Culture, so Moranis isn’t entirely against revisiting his old films.