The words "crisis" and "critic" are both derived from the Greek root "krinein", meaning, "to separate, decide, judge". In his Basic Problems of Phenomenology, Heidegger puts this notion at the root of his famous "ontological difference".
—the differentiation between being and beings. Only by making this distinction—krinein in Greek—not between one being and another being but between being and beings do we first enter the field of philosophical research. Only by taking this critical stance do we keep our own standing inside the field of philosophy.
It is in precisely this sense that Beckett thought that Heidegger was "too philosophical":
What is more true than anything else? To swim is true, and to sink is true. One is not more true than the other. One cannot speak anymore of being, one must speak only of the mess. When Heidegger and Sartre speak of a contrast between being and existence, they may be right, I don’t know, but their language is too philosophical for me. I am not a philosopher. One can only speak of what is in front of him, and that now is simply the mess. (In conversation with Tom Driver, quoted in Marjorie Perloff's Wittgenstein's Ladder, p. 135)
Those who want to know what Beckett might have meant by "mess" should read, I think, his fascinating novel How It Is, which describes, precisely, how and not what it is. It is a book that operates with no ontological difference at all, or at least a very minimal one. In that sense, however, it is also an argument for making such a distinction, for being critical. How It Is really is a mess. The form of life it describes, the "existence" it implies, is a groping around in the dark; as literature it is barely articulate, a "murmur[ing] in the mud".
To be critical is to distinguish among things in a way that transcends their particular thinghood. It is an attempt to situate any particular thing in a larger category of things, not just to register that this thing is here, but to determine its kind. The ultimate version of this is criticism is what Heidegger calls philosophy: the moment when we distinguish this thing that is clearly from everything that is not.