How many composers of music are there today? How many people write? How many people are there in countless fields of endeavor compare to 50 or 100 years ago. I'm simply stating that just because there are more doesn't make them better, more importantly doesn't make the average better. 50,000 people with songs on youtube-how many Beethovens or Mozarts are there? 100,000 people taking writing classes-how many Shakespeares?
Genius comes along once in a generation or once every few generations.
There were always more geniuses than people in the 1500s knew of, but they never heard from/of 99% of them. Most of them were slaves or peasants, couldn't write or read, couldn't board a boat or a plane, or simply didn't live in the few areas of Europe whose dictation of history we now accept. You don't think there were dozens of Aztecs who could have played the piano as well as Mozart but were born into a world that hadn't conceived of instruments?
Humans aren't necessarily genetically "better" today, but they certainly have more opportunities to make something out of their genetic gifts.
Why not Hagan? Or Vardon? Or Taylor? Or the Morrises? You're drawing a line too, as we all are, but you've yet to provide any reason for doing so.