Extroverts have a hard time understand introverts because they thrive on interacting with others (even strangers.) So the more, the merrier. Introverts are the opposite. Groups are exhausting for us. I was both an introvert and shy most of my life. Parties were torture for me. I couldn’t do “small talk.” Which made me uncomfortable, and it showed. Which made me less approachable. Although people still tried.
But a career change (teaching guitar) forced me to learn conversation skills (asking questions, listening and responding, giving more than one word answers) and I gradually became less shy. I don’t really consider myself shy anymore. Although it flares up occassionally. I don’t mind group activities nearly as much because I can usually hold a conversation now. And I am fairly comfortable interacting with strangers. But I am still also comfortable being alone.