Here's your sign.

And your argument isn't subjective?

Please tell me, then, how the gameplay changes quantitatively by a change in a game's graphics.

Graphics only equal gameplay up to a point. Yes you need some kind of graphical interface to play games, but once a certain level is reached, improved graphics are simply added eye candy which doesn't improve how battle are fought, cities are improved, or units move around. The best graphics in the world don't make the gameplay any better or worse then what the game is at its core mechanics. It makes it nicer to look at the first couple times, but after that if the underlying mechanics aren't there, niether is the gameplay.

Hence why, if Hortz had been talking about graphics as related to strategic zoom, I would be in complete agreement with him.  BUt he's not talking about, for lack of a better phrase, 'functional' graphics, he's talking about pure eye-candy.

Thank you for getting my point

That said, while the actual 'core' graphics of the game are of lower priority, you screw those up enough and the UI can't help.  For example, dark green squares representing troops, on a light green field of 'grass'?  Really hard to see!