Don't you know the sky is falling? The haters go through the same old idiotic song and dance whenever a new Civ game is released.
If they made incredible graphics that only 20% of people's computer's could use then 80% of their potential customers would be SOL. The fan base would erode and potentially there wouldn't be a Civ 6. That would be an unwise business decision. Is this really a hard concept for some people?
poor code would make it so people wouldn't be able to run the game on they're computers, not beautiful graphic design.