Greeks were both Europeans and lived in an agricultural society. If you go to the research, you will see that hunters-gatherers obtain 70-80% of their calories from meat. And the don't have baldness, diabetes, Alzheimer's, etc.
Look what happened to people when they started eating grains and sh*t like that. Craneal capacity dropped, bone density dropped and stature dropped, all symptoms of malnourishment. Do you know another symptom of malnourishment? Hair loss due to uncontrolled autophagy in an attempt of the body to obtain protein.
Agriculture started 12,000-20,000 years ago, there is no evidence that European hunter gatherers before than did not go bald. All the illnesses that you describe have a huge genetic component. There is more genetic variation between two modern south African hunter gatherers then a French and a Japanese person who from a genetic point of view a practically siblings.
If diet was as big a factor as you claim then it would affect children and there would be huge correlation between what you eat and hair quality, yet there is not.