What is missing in the above response is acknowledgement that there are mountains of books and gigabits of websites produced in thin fonts in reduced-contrast color that contain no meaningful hierarchy of emphasis. Emphasis can be signaled by position, font size and weight, borders, and other attributes that don’t compromise readability.
Graphic designers must acknowledge that beautiful, unreadable text should generally be reserved for use in wedding invitations and placards in art museums, where the information is either so unimportant that it can be ignored, or so vital that the user will make a strong effort to make it out despite its lack of readability. The more aggregate hours people will spend reading a composition, the more important is readability versus style.
Reducing contrast and selecting font width and color are demanding tasks which should be assigned to only the most experienced, highly educated designers. They are not for the web designer with an AA degree to play with.