That's an easy one. It's a major.
What a difference it would have made in everything we need to learn in life: how to make good decisions, handle relationships, financial management, find & keep a good job, buy a car or home, how to keep from learning all your lessons the 'hard way' and possibly save yourself grief & guilt over screwing up so many times along the way.
I'd love to have found my mother. Or even my father. Foster homes & orphange upbringing are certainly no replacement for the true guidance & direction, not to mention the love, loyalty & attachment, one gets from a real family.
When the one person who is to love you & care for you from the beginning does not, your entire life lacks direction. Adding to it, the JWs will never know what pain & grief they cause by their shunning tactics.