Fuzzy-looking chyrons: what causes them?

What makes on-screen titles, pictures, etc, produced by a Chyron device or otherwise video-graphic display hardware, etc. appear fuzzy and moving along the edges, especially on programs from the mid-60s to the mid-late 80s? It seems when such a graphic is used nowadays, it doesn’t look as fizzy and frayed on the edges as it does on these old programs.

The old matting technique was just to color a given pixel a specific color, based upon whether it’s the foreground object or the background object. Because of the way that TVs work, doing that causes flicker on the horizonal borders and fuzziness on the vertical borders. Better yet, when a line was diagonal, you got both effects. Things were done like that because the computation necessary to do proper filtering would have made the device very expensive to do so in realtime.

Nowadays, with the huge improvement in electronics, it’s possible to properly filter the foreground and background objects to remove the flicker while improving the sharpness of the graphics.