From running my own apps and toy startups in college, I don't think its really the age, its rather the ability of the person to do many things from the tech side to the business side from like creating the tech/app to going out and marketing it so you can actually carry the app to success at an early stage, the experience the person actually has with developing and marketing/distributing a product so you can carry the app at a growth stage, the connections the person has to raise money and find cofounders/employees and the financial capital of the person so you can scale a product to and past product-market fit. These things can come with age but a young person with all the above can run a successful business if they have these things.

On the other hand, you can be middle-aged or 50+ and not have any of these things and run a quite awful startup that turnovers like ~20% of your employees each month which my friend works at and can attest to, as they have a rather middle-aged senior management and ceo + cto at their 50-person startup with executives who have been in the tech and real estate industry at companies like Expedia for 7+ years and it is not successful despite raising huge amounts of cash and their company product has never been launched in the 2+ years or any user testing in the period their company has existed and still offer free dinners and monthly bonuses with the enormous cashpile they raised and keep raising.

This is also why I think people like Mark Zuckerberg or Steve Jobs/Steve Wozniak or Bill Gates or Spiegel/Murphy or the Collison brothers, etc. has, which is the ability and experience or at least talent of pretty much any middle-aged startup founder. There are just some people that outshine others even at a young age.