"Thing is, older people can be hidebound: stuck in ruts."
They can also be brilliantly innovative and experienced. Something that is literally impossible for the young. Sure, sometimes you get some child who sees something because they don't know the literature or history, but to say it's a young person's game because of that? Having worked in the software industry for the best part of two decades, I can count on the fingers of one hand the number of inexperienced programmers I've met who are better than people with many years' experience. It does happen, but by and large the better programmers are the ones with a lot more experience and knowledge.
The exact same thing is true of architecture. Is that a young person's game? Also surgery. Also electronic design. Also journalism. Also medicine. Also music. Also this, also that, also almost every skilled profession there is. The only true exception I can think of is pure mathematics in which the genius steps do seem to come from the (relatively) young, but that is something that can be done with zero knowledge or experience, unlike hammering on someone's network.
If we say that security research is a young person's game, by the same criteria we have to say that almost every skilled profession in the whole world is also a young person's game, and that's just nonsense.