You CAN assume that, but it takes a lot away from Thanos to do so.
Do we actually know what the DotM is in the cosmic hierarchy? It seems to take credit for stuff that other cosmics have done, like Thanos killing the modern Titans. It does seem to have corrupted Moondragon and it's the only candidate we have for the murder of the original Titan inhabitants, of whom Sui-San is supposedly the only survivor. And it's an old enemy of the Earth Eternal Interloper, who's a weird character in and of himself.