But that was just a cameo of him wishing Spock a happy birthday long after he was dead. We need him to be back alive.
Oh it was so much more than that. His narration carried the film to it's conclusion and helped to (in my view) better tie up the themes of friendship. Older Spock talked with Younger Kirk, and Older Kirk (via message) talked with Younger Spock. Informing both younger selves of what the other would come to mean to them. It's a shame we never got that, because I think it was damn compelling.
Now, I just don't see the point. There's nothing an older Kirk could contribute to a story now, really. Except to undo the bad ending he got in Generations, which isn't quite enough. That's a fan reason to want him back.