But... that is exactly what this show is. The drama of trying to survive in an otherwise hopeless world. There are no large, safe, scientific cultures left (that we know of), and certainly none that have the training or resources to work on finding a cure. It's 100% survival for the sake of surviving. The last person qualified to tell us whether or not there is a cure died in the first season, and the only news he had worth reporting is that everyone is a zombie already anyway; they just didn't know it yet.
If anything, the end game of this show is the witnessing of the end of the human race. Changing that in any way would turn it into something completely different.
And that's all its been since day one. It was never a story with any other ending in sight. Just the adventure of this one group of people enduring through a no-win situation.
Which, again, is like most shows out there to one degree or another. Star Trek: TNG
never had an ending. There was a finale, sure, but the characters and the world continued on after that finale. Modern Family
certainly has no end-game in sight. Hell, even shows like Homeland
don't. Once they thwart the current attack on the US, the CIA and the world/show will continue on. Once they capture/execute Abu Nazir, the CIA and the world/show will continue on. Once they reveal Brody to the world, the CIA and the world/show will continue on. Once Carrie, Brody, Saul, David, Mike, and/or all their respective families are executed, the CIA and the world/show will continue on. etc. Or is there some definitive end to these shows that I'm just unaware of?