Based upon:
Example for "crunch" --
"crunch" is simply game-mechanical content. The degree to which a game is "crunchy" is the degree to which its published material focuses on mechanical, rather than descriptive or narrative, presentation." (Stephen Lea Sheppard)
http://forum.rpg.net/archive/index.php/t-184852.html
Example for "Renaissance" --
"The word Renaissance, whose literal translation from French into English is "Rebirth", was first used and defined by French historian Jules Michelet in his 1855 work, Histoire de France...The Renaissance was a cultural movement that profoundly affected European intellectual life in the early modern period. Beginning in Italy, and spreading to the rest of Europe by the 16th century, its influence was felt in literature, philosophy, art, music, politics, science, religion, and other aspects of intellectual inquiry. Renaissance scholars employed the humanist method in study, and searched for realism and human emotion in art."
https://en.wikipedia.org/wiki/Renaissance
And, applying those concepts to a gaming context with its own (historical) periods and influences, my very first reaction is that "crunch renaissance" alludes to:
...a re-imagining of game rules of relative complexity into a more aesthetic and effective (organic or reality-based) presentation--including by re-visiting profound principles and insights of earlier systems.