What you see as a deficiency in the "Church" is simply the same deficiency in carnal men that was there long before Jesus died on Calvary and it continues today. It continues not because God is unable, but because men, even probably many men who started out right with God, having grown weary in well doing and having taken their eyes off of Jesus, walk their own pathway and call it His.
"Woe unto them that call evil good, and good evil; that put darkness for light, and light for darkness; that put bitter for sweet, and sweet for bitter!" Isaiah 5:20
Many bearing the label of Christian do this and teach others to do this and then some say as you do here 'if only they did it better...'? Certainly if everyone fully submitted themselves to God and did so continuously this society on planet Earth would be better... but God sees this better than we do. His plan is on the right track. The improvement of the earthly societies or church group of men via the Church is not really His ultimate goal, is it? Again back to what Apostle Paul wrote:
"For now we see through a glass, darkly; but then face to face:..." I Cor 13:12
That "face to face" vision is not an empty promise. It is what is coming to pass in people. The only question for each person within himself is, 'am I or am I not to see that or do I'? In spite of what some on this forum will say, the answer to that question is up to each of us. God through His Son has made it a possibility, but too many looking at the frailties and weakness that they see in themselves and other men, continue to deny the possibility. They deny the power of God and to any one who claims to have it or that God is working on it in them they call such people on the carpet before themselves... as if they should have the final say.
"Where there is no vision, the people perish..." Prov 29:18
Long before Jesus was born to Mary, David wrote these words:
"When thou saidst, Seek ye my face; my heart said unto thee, Thy face, LORD, will I seek." Psalm 27:8