(spoilers) my preferred ending: cooper is trapped in the tesseract, each moment of his daughter only plays once, he futilely panics and darts moment to moment trying to reach out to murphy only to be seconds too late. The tesseract closes around him as he’s trapped into one last one of those moments. The screen brightens as he gets one last glimpse at his daughter’s face before a fade to white. bonecrushing, but maintains the message better. Every moment is precious.
you can’t drop lines like “nature is never cruel” and have cooper ignore every sign from his daughter, the “ghost”, and the universe itself and then just give him a “happy ever after”. Not to mention how many times it was drilled home that once you’re cross a singularity you’re trapped forever and they just immediately undo that.