I think you have a valid complaint. In the first place WRI should settle down with their fonts and keep them fixed from version to version. And they should use more taste than they do. How many people like all Red headings in the Default style sheet?

You can always change the font for Text cells. Here are some fonts available on Windows that clearly distinguish between capital I, small l, and the numeral 1: Calibri, Constantia, Book Antiqua, Georgia, Tahoma, Segoe UI (which I think is used in Panels), Verdana,