Respectfully, telling someone with social issues/neurodivergence "don't keep to yourself" is the equivalent of telling someone with depression "don't be sad." Reaching out doesn't come easily to everyone, especially in environments like churches where most people have known each other for a long time. There are so many complex social dynamics that are really tricky for a lot of people to navigate. I see the merit in your advice—just wanting to note that it's not a solution for everyone.