I think that a lot of people here are confusing "introversion" with having social anxiety.
Being an introvert doesn't mean that you're scared of socialization. It means you generally prefer quiet time over socializing.
From Merriam Webster:
A person whose personality is characterized by introversion : a typically reserved or quiet person who tends to be introspective and enjoys spending time alone.
You can be both, but they are definitely not the same thing.