I don't think it was "left out", it was purposely omitted. By actively forbidding any sort of public critique or debate over doctrine, any religion can sow the seeds of its own destruction. A good example is the pre-Reformation Catholic church, which punished anyone who actively questioned the pronouncements coming from Rome. Luckily for all of us, the Catholic hierarchy has kind of caught on over the years.
Quite a few Protestant denominations have no central church hierarchy. They do, however, have voluntary organizations which police their member congregations.
A hierarchy is not necessary. The police function absolutely is. AND a healthy debate over doctrine and Kuran interpretation will also help in policing "heresy".
No intention to insult any Catholics here, but from the standpoint of openness and toleration of debate, Islam is where the Catholics were pre-Reformation. Islam needs a reformation.
Islam does need to reform, if it can. If it can't, then it will either fade away gradually and peacefully or suddenly and violently.
But looking to a comparison to the Christian Reformation is probably not a good idea. The Reformation was a fundamentalist movement in response to the overly worldly and corrupt Church. The Muslim fundamentalists have a greater claim to being the reformers of Islam as they are seeking to, as they see it, return purity to the religion. The liberal and secular Muslims are few in number, intimidated, mistrusted, and at risk.