Used to be people learned how to cope with criticism as they grew up. Now we have situations like a play where everyone’s the lead. The world gone mad.
Social shyness is not caused by criticism and feedback but actually from a lack of it. The shy person doesn't know what they are doing wrong and people are too polite to tell them. So they just give up and avoid situations they do not understand. Social shyness is improved by feedback, coaching, and constructive criticism. But that is really hard to come by without a network of many close forgiving friends which shy people do not have. The internet is adding to the problem in many ways but helping in others.