Correct. It's great for mostly text content or as a nice quick and dirty fix until you get around to creating a proper dark theme.

Alternatively you can target elements individually, omitting images.

Perhaps there is some fancy selector which excludes images?

If you use just invert(100%), no grayscale, on the body, you can add img { filter: invert(100%) } to reverse images back to their original color. However, if an image has any transparency or translucency, it may be harder to see with what the background color has become.