No amount of cleaning (the keyboard) or hand washing is going to stop this until Apple uses a material that doesn't wear down as easily.
Those are good points. There's no such thing as a plastic that won't ever shine. They all will because all of them get worn smooth eventually by constant friction with your fingers.
But... if my experience is any indication, I do think Apple has finally started using a coating that doesn't wear away so easily. After 9 months of owning an M4 MBP, my keys still look almost new. The area where my palms rest are actually looking more worn than the keys.