Christians should be accepting and respectful of traits of introverts. Christianity is one where love for others is very important, and loving others includes allowing others to pursue what they enjoy.
Often people in their excitement to get a group at church going expect everyone to come to large groups and enjoy it. An introvert might not. Being in a big group is usually not fun to introverts. It's often exhausting: It's too much information all at once—an introvert loves to think about each idea, and often feels exhausted after large group meetings and parties where hundreds of ideas are thrown out there.
Even worse is if a person looks down on someone, or if a person is hard on themself, for not constantly going to events and parties, when really it's very often a matter of indifference. There is more than one way to get to know people, and being in a large group doesn't have to be the only option.
A person might look down on an introvert assuming that introverts don't care about people. But that's not true. When introverts are not with people they still like to think deeply about people and life and things. Talking with close friends is something they love.
If a person doesn't go to your event, the reason most likely is not that they don't like you or people. They just might not prefer being in a large group setting at that time. You might love the topic of the event or love being around lots of people at once. And that is good and fine, but you can't expect others to have the same preferences as you. Introverts at times do want to venture into large groups—it's a great way to meet people who might become close friends, something introverts love—so it's worth inviting them. But expecting them always to come isn't good.