What Schrödinger’s cat REALLY means

@10:40 "If you never open the box, then you'll never know whether it's dead or alive."

Not true; the state of the box contents is entangled with the rest of the universe in many many places. Most obviously with the person who packed the box, but also more fundamentally with the energy states of the photons that bounced off it before it entered the box.

That's the flaw with Schroedinger's Cat thought experiment; it's impossible for a macroscopic object such as a Cat to enter a box without becoming entangled with some aspect of the surrounding universe.
Moreover it's impossible for the box itself to create perfect isolation between the exterior & interior of the box; we as observers are already entangled with the state of the Cat.