The term "theorists" is generally, 'within the literature', meant to refer to critical theorists. Specifically, this term usually refers to the Frankfurt School of thinkers, intellectually led by the famous theorist Theodor Adorno.
Critical theory is an ambiguous discipline, but is most generally an anti-systematic, anti-institutional, and anti-scientific analysis of common cultural phenomenon. Anything from the meteoric rise of McDonald's as a paradigm for food consumption to the Reagan Presidency to the notions of truth employed by contemporary philosophers is fair game for critical theory.