In my humble opinion only small part of modern Christians may be called as True Christians. They can be in any church, even in dead ones ( s. Revelation ).
Only Fundamentalist Independent Baptists ( not Southern Baptist ), some other Christian Denominations ( even by Jehova Witnesses) , small parts of Catholics and Orthodox are still alive.
The small rest of True Christians from all denominations shall begin to unite themselves in an independent Christian Fundamentalist Movement to withstand Devil and follow the Teaching of Jesus.
The program of this movement can be only one:
The Holy Bible
You may be being a bit too hard on modern Christians. Many, most, sincerely love God. One of the problems is that they learned the Bible as children, and they learned it from the perspective of modern English and modern culture. By the time they reach their twenties, they have heard these stories all their lives and sincerely believe they understand them.
The Bible takes life-long study. It also takes the study of Biblical languages, cultures, and histories. Then it takes more study. Telling people they can read and understand the Bible on their own is a bad mistake--and it leads to atheism--and worse, it can lead to hatred of God and people of faith.
It takes
discipline, not a murmured "I believe Jesus is my savior. Now I will be in heaven." It takes
work, which is a word that absolutely horrifies many Protestants. I am not speaking of earning or working one's way to heaven. I am speaking of following The Way of Kingdom Living each day of one's life. People who believe they don't have to do a thing because Jesus was already punished for all their faults haven't a clue. Jesus taught us to discern and then to follow the will of the Father, to be aware of the people in our immediate surroundings and to help
them. He warned us that when we fail to help them, we fail to help him--and failure to help those in our immediate vicinity who are in need--is a failure to help him. Christianity is a way of life--not a stamped pass into heaven where they imagine themselves singing, "I never lifted a finger."