As someone who was (and sometimes still is) intensely introverted, I think the grandparent post was simply nudging toward the fact that introversion can be stifling and is, in that sense, often unfortunate. In my view, anything that limits one's options is.

I'm happy as an introvert being alone, but I'm happiest when I don't have the requirement of being alone to enjoy myself. KnowwhatImean?

When it becomes an impediment (or inconvenience) to staying healthy, a person would be wise to not assume themselves permanently incapable of operating outside their current, relatively confined comfort zone. I think this is true in all areas of life and adapting/learning.