It depends how important suspense/mystery is to the story, and if you enjoy suspense/mystery.
If you enjoy suspense, and a story is elevated by suspense, then spoilers matter.
If you don’t care about suspense, then spoilers don’t matter, and you don’t appreciate when a story makes use of suspense (nothing wrong with this, people can like different things).
It depends how important suspense/mystery is to the story, and if you enjoy suspense/mystery.
If you enjoy suspense, and a story is elevated by suspense, then spoilers matter.
If you don’t care about suspense, then spoilers don’t matter, and you don’t appreciate when a story makes use of suspense (nothing wrong with this, people can like different things).