Sounds suspiciously similar to talk about the mental inferiority of the 'Noble Savages'...
From the 7th until the 11th centuries, there was lively theological debate in Islam and different schools of thought arose. Beginning in the 11th century, though, it was held amongst Sunni scholars that "the gates of ijithaad [sp.?] are closed." This meant that no new interpretations of Sunni Islam were permitted. So, yes, Sunni Islam, which the majority of Muslims at least nominally adhere to, is still stuck in the early middle ages.
Interestingly enough, the Shiites, now dominant in Iran (and in the future possibly dominant in Iraq), never closed the gates of ijithaad.