When famous abstract painters/artists creates a piece of artwork that is sub-par, are most art critics able to objectively conclude as such?

Answer 1

The simple answer to this is some can and some can't and still you can make an argument about each one. This question is posed in a way that is condescending to the simpleness of abstract painting. The phenomenon of people in a gallery/museum who say my kid could paint that. It's because there is a conceptual element to it which some folks have a hard time grasping. One art critic may attack the aesthetics while another defends aesthetics with conception. Still, it's not always significant what the critic thinks or chooses. It is the name brand galleries which are the tastemakers. The museum who exhibits it and the publics reaction and evolution of reaction is what matters and gives the artwork it's aura. Critics praised cubists which no longer are as culturally relevant as Baroques and Picasso. Artwork is revisited, sometime monthly, yearly, decades, centuries. Perspectives shift. Yes a critic can generally tell if the work is poorly made but No they don't know if it's a lasting work of art.