No, no, no.
The guillotine is not medieval. While there were some predecessor devices that were, the guillotine came to be during a debate of the parliament that produced the French Revolution. Its association with that revolution, and especially its frequent use during the Terror, made it a symbol of the Age of Reason and the Enlightenment.
As a member of the assembly Guillotin mainly directed his attention towards medical reform, and it was on 10 October 1789, during a debate on capital punishment, that he proposed that "the criminal shall be decapitated; this will be done solely by means of a simple mechanism." The "mechanism" was defined as "a machine that beheads painlessly". His proposal appeared in the Royalist periodical, Les Actes des Apôtres.So it was all about reforming the law to eliminate distinctions between classes, about bringing reason and science to bear on social problems, and about reducing the pain and cruelty of the death penalty (with an eye towards its eventual abolition, as France did in 1981). It would be ironically appropriate for the Enlightenment's foremost weapon to be brought to bear against ISIS.
At that time, beheading in France was typically done by axe or sword, which did not always cause immediate death. Additionally, beheading was reserved for the nobility, while commoners were typically hanged. Dr. Guillotin assumed that if a fair system was established where the only method of capital punishment was death by mechanical decapitation, then the public would feel far more appreciative of their rights.
Despite this proposal, Guillotin was opposed to the death penalty and hoped that a more humane and less painful method of execution would be the first step toward a total abolition of the death penalty. He also hoped that fewer families and children would witness executions, and vowed to make them more private and individualized. It was also his belief that a standard death penalty by decapitation would prevent the cruel and unjust system of the day.