How well does Instagram improve old digital photos?

More than 10 years ago the pictures I took with my first digital camera were of lower quality for obvious reasons (and I’m not talking about the numbers of pixels, but clarity, colors and other factors).

Would Instagram be an option to improve their quality? Any experience with it? What about doing this on a PC? I heard about an application called Instagrille. Is there a batch mode handling entire directories of jpg-files? Is sharing mandatory?