That said:
https://techcrunch.com/2009/09/07/when-it-comes-to-founding-... The average age of startup founders is older than the press makes it seem.
I talk to people in each new batch of Y Combinator. The general consensus is that the average age of the founders seems like it is increasing as they fund harder and harder tech projects.
I coincidentally recommended a 58 year old founder about 18 months ago and they were interviewed.