There's no need to replace it. TNG was a product of the 80's let us see the ingenuity of the 80's in action.
Well they still need to keep things fairly consistent, I think. If they're going to dramatically sharpen and clean up the planets, transporter beams, and other energy effects (which I am eternally grateful for), it only makes sense to improve some of the shakier model effects as well.
Otherwise they're likely to stand out even MORE.