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.
I absolutely would, my players would need to be creative to allow this dust pile to communicate and do anything, but I'm quite sure they could manage
New villain is a cleaner with a feather duster +1.
I was legit imaging a pile of dust that learns telepathy to communicate with their party members and screams in an angry scotch accent to be thrown at their enemies so that their particles might sting the bastards eyes and blind them
They'd be deathly afraid of any and all cleaning staff, but also the party would have a broom and catch pan of some sort for when their buddy get a lil spilt
I was thinking they might learn or get enchanted with a minor wind cantrip that they can cast on themselves infinite times, and rearrange themselves into words.
They can communicate with any literate character, but slowly, only in words that are short enough. Otherwise they have fo finish the word on their next turn.
If it's genuinely windy in game, the player has to write their communication with their off hand, blindfold whilst someome shakes them or the paper randomly.
Same, I'm now going to try to kill a PC with disintegrate just for the occasion!