How Many Evangelicals Have Separated from Reformational Theology Concerning the Authority of Scripture

 First of all, I don't like to overgeneralize people in religious groups and bash them. The purpose of this post is merely to show ways that many Christian Evangelicals on many accounts, have departed from the theology of the Reformation. 
Sola Scriptura was a key teaching of Martin Luther and the Protestant Reformation at large. At a time when many of the hierarchy in the Roman Catholic Church did not want the common man to have the Scriptures, the early Protestants insisted that the Scriptures were intended for all. Many in the leadership of the Catholic Church felt that the Scriptures could only be understood according to the teachings of the popes and councils. Gradually, the Protestants came to formulate on a doctrine of the Reformation known as Sola Scriptura which said that Scripture is the highest authority. On the contrary, the Council of Trent in the sixteenth century would equate Scripture and Tradition. A key difference between Roman Catholics and Protestants from the Reformation was the role of tradition and Scripture, though that debate is not the subject of this post.  

For years, Protestants have held to the Supremacy of the Holy Scriptures over all other authorities such as elders or pastors. But Sola Scriptura has been largely misused today by Evangelicals though. For example, some Evangelicals criticize Roman Catholicism for following men such and elevating the popes on a level beyond that of other men. Roman Catholicism is not without its criticism of course, some of which I have made in other posts.
As examples to authorities many Evangelicals put so much trust in, when Martin Luther, John Calvin, A. W. Pink and John MacArthur etc. are treated as authorities instead of the papacy. So many Evangelicals may say that Catholics follow tradition but in many respects many Evangelicals do as well though they are often ignorant of this hypocrisy! They preach aloud ''By Scripture!'', but sometimes their own pastors resort to being mini popes over their congregations when they are questioned or disagreed with by a layman. Suddenly, the Apostle Peter does not have the Keys of the Kingdom but so some individual pastors think they do. This is all the danger of ever putting anyone we admire or we are told to submit to on the equality of authority as is found in Holy Scripture. In disputes against heresies, the church fathers of Ancient and Medieval Times usually appealed to Hoy Writ. over the judgments of church authorities.   
Some criticize Catholics for following the pope absolutely but then follow their own pastors as if they cannot err. While Evangelicals may not put their trust in traditions of the fathers, many of them replace such trust in seminaries and college education or traditions they were raised in instead. Perhaps also, many Evangelicals would find it surprising that Seminary was started by the Catholic Church in the Counter Reformation. Yes, a religious institution that so many Evangelicals put so much trust in, originates from the Catholic Church though they reject the Roman Catholic Church as their authority. 

In reality, the Evangelicals that put so much stress and emphasis on where their pastor went to college or seminary, and how much education he has, actually goes against the roots of Reformational Theology. The Protestants believed the common man could understand the Scriptures without the interpretation of a priest. Now however, it is quite common for Evangelicals to recite certain theologians they trust in as having the true understanding of the Scriptures due to their supposed formal training in it. If one is going to put such trust in men, one needs not be a Protestant.
It seems Luther's intent of Sola Scriptura has largely been lost among Evangelicals. They may call themselves Protestants, but in many respects they have left much of what the Protestant Reformers stood for. Protestants may highly regard theologians of the past, but the Holy Scriptures, not popes, not councils, and not education, is the standard to consistent Protestant theology of what is true or false, and what is right and wrong.

Further Sources: Reformation Thoughts by Alister Mcgrath