Everything is wrapped up quite nicely. All major & mid level characters (that are still alive) have all of their big troubles resolved and I can't imagine what these naysayers could possibly be looking for in another season. The Byrds being a happy family laundering cartel money protected by the fbi? I'm not sure all conclusions need to service your moral compass, but in this case they certainly wrap up any pressing drama. Favourite show ever with a fitting end.