I have plenty of 28 to 35 year olds in my workplace. 30 most definitely is NOT the new 50 in terms of workplace power and authority. At least in my industry. There are some 50 year olds who are duds and aren't going anywhere. But none of the 30 year olds have the skill and knowledge to be in charge. Many are smart and driven, but they just aren't there yet. Maybe this is a tech industry thing.
Maybe this is a tech industry thing. It is not just a tech industry thing. My wife does a lot of volunteer work. At the museums she works for they put these kids in charge of the older volunteers and 90% of them are completely incompetent.
In my company (multinational megacorp), it takes 10 years for someone to just fully understand how the different parts of the company work together. It takes at least 5 years to see several mega projects through their entire life cycles, just to build experience from initiation to decommission.
We do promote mid-career people into leadership positions, but those are growth positions with lots of mentoring and room for failure, not "the new 50."
-PJ