Okay, listen. You don't need to be witty and a jokester to be interesting. You just need to be genuine. It's that easy. Talk about things that interest you. Don't try too hard, it may come as insincere or fake if you do. If you don't get the joke a friend told, then it's no big deal. If you can, tell them you don't get it. Maybe it's an inside joke you're not a part of. Try to have one on one conversions with people. You don't need to participate in all of the group discussions. Sometimes it's ok to just listen. I'm also an introvert, I get exhausted by people pretty quickly. But what helps me is I'm upfront with my friends and they are too. If I don't feel like interacting with them, I just tell them. They understand, they're my friends. You do what's comfortable to you. It's fine. But sometimes it's good to get out of your comfort zone and try stuff before you cross it off your list before even attempting it. A little courage is required, but we all have that within us, right? And no 23 is not too old for anything, don't listen to anyone who says otherwise.