Vulnerability imho is synonymous with gullibility. It is not a sign of maturity; because, too often sympathy is given to people who deserve the hard-core truth of reality.
The vulnerable are gullible to people who prey on this 'weakness'.
In my personal opinion, the gullible/vulnerable lack a certain amount of inner maturity of embracing tactfully, what I call the 'telling the truth, shaming the devil' principle...lol...
Peace.