Disclaimer: this is purposefully obtuse.
Other effects in the game which explicitly state they kill you:
Shadows, succubi, massive damage, death saving throws, beholder death ray (notably not even their disintegration ray kills you), power word kill, vampires, mind flayers, night hags, drow inquisitors.
Clearly, if they intended for disintegration to kill you, they’d have said so. Since specific overrides general, and there is no general rule that disintegrated creatures are dead, I rest my case. QED.
Wanna bet?
I’d make it an absolute realistic pile of dust, unable to move, unable to cast magic, fight, or anything but be carried along by whatever picked it up, and when enough of the dust gets separated, death is automatic.
But I’d still allow it as an interesting edge case once.
