designers are so different from the majority of the target audience, it’s not just irrelevant what you like or what you think is easy to use — it’s often misleading to rely on such personal preferences.

This is so true. What's trendy right now is light grey print and even fainter input boxes for addresses,etc. For old people,with poor vision,it's often a case of not even being able to find the input boxes. The faint gray box around where I'm typing this is a perfect example.