AFAIK original sin does teach that all men are fallen and require salvation. This doesn’t mean that human nature is all bad and it’s indeed not the same as total depravity. However it’s also not true that men are born holy.
Original sin is a deprivation of these positive qualities. Mary, for example, preserved in holiness, not simply cleansed of it. Holiness is our natural state, and so baptism returns us to that preternatural holiness that Adam enjoyed when he walked with God in the Garden.