Holding executives responsible for the quality of their people is critical to an organisation's performance. Talent should be the responsibility of the whole business; it is too important a resource to be confined to one department.
There are lots of books and there's plenty of research into this topic but a 'Talent Engagement Venn' is primarily based on personal experience and opinion. It's not an all-encompassing solution or a cure for all ills. However, it is worth trying and can produce interesting and useful results.
In my own experience, not all young people that I encounter from the millennial generation are actually brimming with self-assurance. Issues of self-esteem, anxiety, etc, are commonplace. That old demon: lack of confidence, holds some of them back.