I don't see the problem. At that link, the browser column is higher contrast. Switching to the Stix fonts gives characters that look more like the TeX column, but seems to be missing a few things. I did not try all the font options.
Really? Maybe it renders differently for you, because here the difference is stark. People keep using TeX so maybe most people don't see a difference. For me, almost every TeX document seems to use a font that looks like something very old and unprofessional. But perhaps as suggested elsewhere it is optimized for higher resolution output devices.
