When the early apostles planted a church and over time prepared to leave, they appointed multiple elders to be the bishops or overseers of the local church (Titus 1:5-6). That apostolic ministry then followed up with those local churches as to their welfare and growth. After the early apostles died, the church began to replace the apostolic ministry with a man, appointed as a bishop, to oversee multiple churches in an area. Soon the position of elders and bishops were separated. This was another doctrine that the church, over time, developed.
We read in Revelation 2:6,15 about the deeds of the Nicolaitans. “Nico” means to conquer and “laos” means the laity. Their deeds were to conquer the laity. Mark 16 says, “And these signs shall follow them that believe.” It does not say that the signs will follow only a special ministry. The great commission is for every believer to be a part of. Instead of the Holy Spirit leading each and every local church through the local elders with the gifts of the Spirit working in every believer, it was the bishop that asserted control over the local churches in his area. God hated this doctrine and so do true believers.
This is one more doctrine the church developed over time. Instead of obeying the teachings of the apostles and lining up with them, they developed layer upon layer of bishops, archbishops, cardinals and popes or patriarchs. The call goes out in the last days, return to the original faith. Depart from all man-made systems.