Citizen Kane has a powerful message.
Charles Kane’s “last word”(s) was “Rosebud”. It was the brandname printed on the sled he’d had when he was a boy. When he got that sled in his youth, it was the last time anybody had loved him. His father, or grandfather?, was briefly shown having a love for the boy.
At the end of his life Kane realized he had never been loved since boyhood because he hadn’t loved others. And the movie says not a word about spiritual beliefs, implying Kane had none. Thus, his life was a total waste.