Church growth is not important. God is the one calling and developing the small, true church. Increasing church attendance will not increase the true church nor will it convert the world. Only Jesus and His bride will be able to convert the world during the resurrection. Then “all the nations you have made will come and worship before you, Lord; they will bring glory to your name,” Psalm 86:9.
The true church is considered a little flock of faithful believers. (See Luke 12:32.) Jesus said,“…many are called, but few are chosen,” Matthew 22:14. “But small is the gate and narrow the road that leads to life, and only a few find it,” Matthew 7:14.
Did Jesus mean that only a few would receive salvation? No. Jesus redeemed all mankind when He died on the cross. 1 Timothy 2:5-6, “For there is one God, and one mediator between God and men, the man Christ Jesus; Who gave himself a ransom for all, to be testified in due time.”
God’s plan was to first open salvation to those who would follow in Jesus’ footsteps of self-denial and suffering. Many (the Jewish nation was called, or invited, to the wedding and failed, except for a few) are called (the call has reached millions during the last 18 centuries, but comparatively few have cared to accept the invitation). Few are chosen (begotten of the holy Spirit and adopted as spirit-begotten sons of God).
That small number who are called, chosen, and faithful are called the church or the bride of Christ. They will receive a heavenly resurrection and will receive the divine nature. (2 Peter 1:4)
After the church is complete, the world will receive salvation during Christ’s 1,000 reign. They will need to develop Christ-like characters and learn to obey.
“They shall not hurt nor destroy in all my holy mountain (Christ’s kingdom): for the earth shall be full of the knowledge of the LORD, as the waters cover the sea,” Isaiah 11:9. “And all thy children shall be taught of the LORD; and great shall be the peace of thy children,” Isaiah 54:13. Finally, “God shall wipe away all tears from their eyes; and there shall be no more death, neither sorrow, nor crying, neither shall there be any more pain: for the former things are passed away,” Revelation 21:4.
For a more detailed study on the true church, please download the free PDF: "Why Are You a Christian?"