Constantine so changed the church that studies of church history tell of history before and after the Nicene Council. It was the great divide.
Yes, and Constantine was the antichrist who changed tactics. The Roman Emperor before Constantine attacked the church through persecution. They attacked from the outside in. But Constantine changed the method of attack. He began the infiltration of the church with false teachers and teachings. He formally began the attack from the inside out.
You have to break completely from the Roman church. Many denominations are still in the same "one holy catholic and apostolic Church" that Constantine built. The spirit of the Roman Church is the source for the many, many false teachings and divisions.
The Book of Revelation gives us the revelations we need to unveil these truths. But the false teachers have come and taken the Book of Revelation from the church. They have led the church to believe that for Revelation chapters 4-22 "none has yet been fulfilled". Don't believe this false teaching.