I don't really think the Renaissance was a pervasive or broad enough intellectual movement to be considered the key figures in the modern conception of the Middle Ages, especially as many Renaissance thinkers still drew largely on Medieval thinkers to form the basis of their own thought (to the degree that I'm inclined to suggest that "the Renaissance" is not a particularly useful bit of periodization for most fields of history).

Instead, I'd say that most of the current mistaken perceptions of the Middle Ages come from three sources. 1.) Protestant reformers who had fairly obvious reasons for diminishing and ignoring the accomplishments of the medieval church and the thinkers allied to it. 2.) Enlightenment thinkers whose entire project largely depended on jettisoning the philosophical tradition of the 1000 (arguably 1500) years which preceded it. 3.) 19th century authors, either as a result of the reasons listed in 1 & 2 or because of the appropriation of the Middle Ages into nationalist and romantic narratives created almost all the misconceptions about the era that still infect us today.

While they probably can't be credited with the complete perception of the period as being devoid of progress, Italian historians during the Renaissance laid out one heck of a foundation. They were the ones who first coined the term that we use now, as a way to separate themselves.

Flavio Biondo was one of the first to do so, seeing the period as distinctively different from his own. Biondo’s contemporaries and immediate followers gradually formalized with terms such as media tempestas (1469), media aetas (1518), and media tempora (1531). The actual term medium aevum is first found by at least 1604 and makes its English translation debut shortly thereafter.