The game has always been as deadly as the DM wants. The DM has unlimited dragons, can double tap, can disintegrate if they want. The DM always determines difficulty.
I don't know why you keep insisting that somehow old school D&D must be deadly. It was easier for a DM to accidentally kill PCs which is why we probably avoided some monsters and types of traps. But avoiding a medusa because it can instantly turn you into stone is not the same as house ruling, fudging or any other claim you want to make.