I don't disagree with your conclusion in general (that a game's choice in graphics should complement the gameplay + other parts of the experience) but do take some issue with the notion of "cashing in". Once I start thinking in those terms, it seems to me that /every/ game is trying to cash in, using various things that appeal to players. New graphics, old graphics, big and open worlds, large casts of quirky characters, minimalistic designs, and virtually everything you can describe about a game is an attempt to get money in somebody's wallet, no? So it seems to me that the main difference between a good retro game and a "cash grab" is whether one enjoyed the game, in which case the accusatory tone comes off as unnecessary.