Christian maturity must be intentional. Growing in grace from babyhood to maturity is the purview of discipleship. God has made provision for His children to grow in grace from one level to a higher level until they attain full maturity in Christ Jesus. Come, Lord Jesus!
To be added to the church one needs to be born again according to the original Apostles’ doctrine and fellowship standards. Unless one is added to the true church of Jesus Christ one cannot grow to full Christian maturity as expected. Come, Lord Jesus!