How central is the claim the pope is the antichrist to Protestant theology?

When I read through Luther's writings awhile back, I noticed he said the pope was the antichrist. I thought this was just some of Luther's usual hyperbolic rhetoric. However, I've learned that many (almost all?) of the major Protestant used to have that as a part of their doctrinal statement. For example, the Westminster confession of faith used to have: > There is no other head of the Church but the Lord Jesus Christ; nor can the Pope of Rome, in any sense, be head thereof; but is that Antichrist, that man of sin, and son of perdition, that exalts himself, in the Church, against Christ and all that is called God. I believe the presbyterian and lutheran churches also used to have something similar. Not sure about methodists, but I have read Wesley claimed the pope is the antichrist. Maybe this was never an important topic for the baptists. So, it looks like until fairly recently (late 1800s, early 1900s) the pope being the antichrist was pretty important for most Protestants. Was that the case? If so, why was it so central? If it was so central, what suddenly changed that made all Protestants cease to claim the pope is the antichrist? Why is it no longer an important doctrine?