Maybe tag it as “deprecated version” or something? Not requesting for the game to be relisted, just that it isn’t removed from the accounts of people that got it. And while the Steam key is appreciated and Itchio isn’t popular like Steam / GOG / EGS, I would presume that, if someone gets a game here, they had the intention of having the game here, not elsewhere.
And regarding having an older version, on a more personal point, maybe I’m on a nicher side, but I like to play old versions of games, even if they’re incomplete.