Rome of John's day could not have been the "harlot" since, as a pagan nation, it was never in a covenant relationship with Jehovah God. Only Israel (Jerusalem) qualified for the designation "great harlot" in the 1st century. Old Jerusalem was the "harlot" who happened to be involved with spiritual fornication with pagan Rome against the Christian church. It was the apostate Jews by the hands of "lawless men" (Rome) who crucified the Messiah (Acts 2:23).
The Reformers saw the spiritual entity we call the Roman Catholic Church as fallen in much the same way as ancient Israel. Rome was in covenant relationship at one time, but had abdicated their position and gone after foreign gods through a gradual process of assimilation of false practices.
Those would be the same guys who said that it was manifestly plain that popes and councils did err.
I'll turn their own medicine back on them: it is manifestly plain (to me) that the "Reformers" did err.
I'll stick with the Bible.
I’ve looked at a topo map.
Jerusalem does not have seven hills.