The bare minimum I described as fully functional is present in Super Metroid. There is only one save slot for each playthrough, loading that one save brings you back to exactly the same game state you last saved. This is perfectly fine.

It's even better to have manual saving to unlimited files accessible through the host machine's filesystem as well as dedicated hardware buttons for an additional quicksave/quickload slot but that all goes well beyond bare minimum fully functional. Autosaves can sometimes be okay as long as they don't overwrite anything.

Soulslikes don't even have the bare minimum save system that Super Metroid has.