Greenberg compares two cultural movements: Avant-garde and Kitsch. Avant-garde is detached from society and politics, at least conceptually. Artists focus on the process of creation (with a lot of attention paid to originality) rather than the content of art. This is contrasted with the concept of Kitsch, which is defined by imitation. Kitsch is the reproduction of the emotions evoked by art without depth or complexity. It is simplified and mass-friendly and does not require intellectual engagement.
Personally, I think art can engage with current situations, be obvious about its intention, and be in dialogue with societal and political ideologies. These things can enrich art by adding layers of cultural meaning. It doesn’t necessarily mean it’s a cheap version of ‘real art’ (Kitsch).