That is not really a good comparison at all. The creator is taking money for his product, while it isn't finished. In this case, it would be more fitting to describe your scenario as you paying the downpayment for a new car, and they give you the bottom frame, with 4 wheels, an engine and a steering wheel, and then smile as they tell you "the rest of the car is coming later. Probably. Unless we don't feel doing the work anymore. In that case you're fucked."
Are you telling me that I would have no right to complain about the state of the car in this case? It is one thing to take/steal an unfinished product, which was never meant to be used in that state at all. If the creator themselves start selling that same product in that state however, it becomes fair grounds for critisism of any kind.