I believe there are markers of spiritual maturity. Some are highlighted in the Bible, and others are practical indicators seen in people’s behavior. One sign that someone is maturing as a believer is their willingness to own their spiritual growth. Related to that is when they begin to take responsibility for helping others connect and grow.
That means they look out for the new person when attending Church. They go out of their way to make a guest feel welcome. They love to speak to new people and shine their light for Jesus. They make it a point to find the person who is an outsider to conversations and seek to bring them into the group. These people make it their responsibility to share their faith everywhere, but especially when people walk in the doors of the Church.
You could flip this over, too. One mark of immature believers is that they continually wait for people to come to them. They want others to serve them. They want others to come and start a conversation with them. They want everyone else to take responsibility for their connection and growth.
Spiritually mature people are not looking for others to help them continually. They seek to help others.