Social anxiety is not a thing that you either have or you don't. Everyone has social anxiety to varying degrees. To claim that people with social anxiety don't live as full or enjoyable lives as everyone else is just plain wrong. What is a "full and enjoyable life"? Is it having an average amount of social anxiety? But then you don't get to do all the cool shit that the people with very minimal social anxiety do. Is it having minimal social anxiety? But then you might end up doing things that you'll regret later i.e. having your silly picture/video go viral and then you might even end up developing social anxiety as a result of the entire world/country/city knowing your embarassing moment.
Anxiety of any kind makes life less enjoyable then not having it. People with social anxiety needs friends, wants to belong in group and generally have normal social needs - except that they are afraid to do necessary steps for it to happen and end up isolated and unhappy. Social anxiety is not the same thing as being happy at home alone and thus not seeking wild parties, it is feeling uncomfortable in presence of people. Happy loners exist, but they don't have social anxiety.
Not everyone has social anxiety just like not everyone who is a bit sad has depression. Social anxiety makes you perform badly on meetings, when talking with your kids teachers, when talking with colleges and in all kinds of situations where it actually matters.
Not having social anxiety is not the same as not doing silly things while drunk. Plenty of extroverted highly social people don't do cool stupid things while drunk.
