The "Reformers" were "Deformers." And none of them agreed with each other about everything. Calvin called Luther a dog and a pig. They called each other heretics. Zwingli was off on his own tangent too. So if you are a Calvinist you think Luther was a heretic. If you are a Lutheran you think Zwingli was a heretic. So the "Reformers" have all been called heretics by each other and by the RCC. So what the heck did they reform? It was not the RCC. But there are many "reformed" churches. Thousands of them. I guess you think that is a good thing?
Luther approved of and admired Calvin's "Institutes of the Christian Religion," and believed the reforms which he set into motion were in good hands with John Calvin in Geneva.
Calvin called Luther "my much respected father who has denounced the darkness of the papacy" and a "great miracle of God."
When Catholics fail at debating doctrine, they fall back on the inconsequential fact that there's more than one Protestant church.
Sola Fide; Sola Gracia; Sola Scriptura.
Like it or not, the Reformers were generally united in their stand against the errors of Rome and their desire to return the church to its roots in Christ.