Lewitt in Progress

1.) According to Lewitt, "it is logic that constitutes the "text"; and the space onto which the art is now to open, the model it is to "picture" and by which it is to be tested by the Mind." To test the mind is something that is not universal as many people have different capacities of thought; however, Krauss states that Lewitt's art is "too simple". My questions surrounds the fact as to whom gets to decide whether a conceptual art piece is "too simple" or "just right"? This form of art cannot be judged based upon the architecture of the art but of the idea.
2.) Lewitt once stated "the idea becomes a Machine that makes the art". This idea is the general foundation of conceptual art, as it conjures the art and is the purpose of the art. Rather than focusing on the visible emotions of a painting or the like, Lewitt provides art pieces that force the mind to conjure the purpose of the piece, however Lewitt also provides instructions as to why the piece was created. Is contemporary art supposed to be a completely subjective activity, in which the audience is left to mentally configure the purpose of the piece? Or is Lewitt providing mental direction of the audiences' interpretation of his art (when providing the written directions)?