Morton might or might not be correct in this view of Heidegger's thinking, for H argued in later essays that philosophy would, or could, and perhaps even must continue beyond existentialism and phenomenology. Perhaps he had in mind the very development being articulated in OOO and speculative realism. My point is that in phenomenology in general it has been recognized that consciousness [the subjective pole of experience] transcends the object/phenomenon at the objective pole of what is experienced. Thus the subject transcends the object and the object transcends the subject in the philosophical sense of the term 'transcends'. Is 'idealism' an accurate category into which to place phenomenological thinking? I would still say it is not since Merleau-Ponty's more fully developed phenomenology still recognizes a transcendence of both subject and object in the Chiasm of their mutual appropriation by one another. Experience of the world still involves consciousness and mind as well as objective structures in/of the physical world in our ongoing thinking of, thinking about, objects -- and that includes 'hyperobjects' in their extraordinary distance from us. 'Idealism' is the wrong designator, category, for developed phenomenology since that term still expresses the notion that we transcend the palpably physical, material, objective world in our mere ideas about it. We can't and don't, and I think Heidegger realized that. Here are several statements from M-P's works that suggest where I'm going (or maybe staying) in my own thinking:
"Just as the perceived world endures only through the reflections, shadows, levels, and horizons between things . . . so the works and thought of a philosopher are also made of certain articulations between things said.”
“Reflection does not withdraw from the world towards the unity of consciousness as the world's basis; it steps back to watch the forms of transcendence fly up like sparks from a fire.....”