Bias toward less experienced but highly technical staff seems to be an artifact of the portfolio management style of the investors and board members. Shotgun investments in a space mean shotgun incentives for managers, which yield shotgun solutions from engineering teams, to whack-a-mole product market fit problems - with randomized, exponential returns.
Profitable, revenue funded companies are more accommodating to the Olds because things like discernment are rewarded. Mature companies (5+ years) that act like startups are as Jerry Seinfeld once quipped, "dressing their best decade." You can usually tell within 15 minutes of entering an office whether it's a place of growth.
Young people are perfect for the former style because they can apply technical know-how without any broader criticism about likelihood of success, strategy, or sustainability. As an old, it can become more difficult to maintain the cognitive dissonance required to thrive in these environments when you have a mental horizon longer than 5 years.
I've worked with olds, and the successful ones recognize the story is no longer about them. They recognize that young people are also like a portfolio of long term investments, so they manage it prudently, and the best ones have learned how to get short.
If you are still doing startups as an employee in your 40s, you are there for the rush and because you love doing it. We should all admit that working for early stage companies is a lifestyle, not a plan. There is nothing wrong with experienced people. They aren't malformed and do not need correction. Some might need more awareness of what they are involved in, but adopting a "fixer upper," mentality is the beginning of death.