I argue that it does look good. Yes, the graphics aren't modern, but it can look very scenic and create a sense of wonder. It could look bad if the grass was just bright green and flat-looking and everything else looked that bad too. I have a hard time imagining people even bothering to play it. Minecraft's art does exactly what it's supposed to do. Here's an example of something very atmospheric created with minecraft blocks. Some might dislike the style anyhow but that's a more arbitrary (though not invalid) preference not related to how well-done the minecraft graphics are.