design isn't a fucking stat, design is a purposeful goal. You're making choices to achieve an end within constraints. There's no 'good design' like a fucking virtue unto itself, you're talking about whether or not this thing that is made achieves the ends you're directing it towards and you don't know what the goals are or the intentions are when you're looking at the end product. You can imagine an explanation but you can't assert Goodness In Design by just pointing at a successful game or even a game you like!
And game design is like that, but harder because the demands of the design include a bunch of competing demands including 'you have to babysit the brains of the worst assholes on earth'
