From 33 AD until the 1554 Schism there was one and only one "Christian" Church, That was the Catholic Church.
At the time of the Reformation; Luther, Calvin, Zwingli, etal... Created about 5-7 "Christian" churches.
For 1500 years there were exaclty four choices:
Pagan
Muslim
Jewish
Catholic
There were no other choices and there were no other Christians, The occasional heresies, but no "hidden" groups
Completely untrue. All throughout the Middle Ages, there were many, many independent baptistic bodies of Bible believers who had no communion nor any history with the Catholic religion. The Catholics tried to suppress them through violence, and when that failed, have continued to try to lie about what these groups believed and practiced, but they were there nevertheless, the true adherents to the apostolic Christianity, instead of the paganised "Christianity" which arose in the 4th century when Constantine tried to unite the various belief systems of the Empire together, which eventually resulted in Catholicism.
I’d be careful there too, there was the Eastern Orthodox Church too, which was a significant part of the Christian faith. The ‘minor heresies’ were also a rather large component, as various sects rose and fell prior to the Reformation.
Be careful telling all Reformed believers they’re wrong, because it’s pretty easy to bring up some papal bulls that have no business existing.
I think you’re forgetting the Eastern Orthodox Churches. Remember The Great Schism? Approximately from 800-1000 A.D.