Eh, for game-released-in-a-disappointing state there’s always two points for me:

1. A personal thing, learn to not buy day 1 or even before. Let other people do that, then avoid ever putting yourself in a frustrated position by simply never buying the broken/unfinished game to begin with. Money - and time - better spent on other hobbies, or well, other games.
2. On a specific level, I always feel that just saying “I’m sorry, but because of X, Y and Z I don’t feel like the game is in any shape to be worth the money asked” and then refunding it is the only real proper feedback to go about it. Voice your reasoning, then undo the purchase to withhold the money. That’s more than enough brain space wasted on an unfinished game you’re not enjoying, anyways.