His philosophy seems to be solely regurgitated from the Greeks

Yeah, I think this throaway claim requires more qualification. No one will deny Heidegger draws heavily from Aristotle&co., and he would be the first to say so anyways.

The idea that "we exist" (dasein) is not a new or profound idea

Sure. But where does he claim that our existence itself is a profound idea? He seems to think we have deeply embedded and inarticulate knowledge of our existence. See, for instance: pg. 69-70 of the Harper edition of B&T/S&Z, where he talks about the "precursive" way that Dasein exists, emphasizing its "averageness" and "everydayness." I don't think he wants to simply state that we exist—yes, the claim is trivial when you put it like that. Rather, fundamental aspects of our existence are "hidden" in plain sight, so to speak. This results from regarding ourselves as entities due to our reliance on a present-at-hand ontology, which likens us to disinterested scientists observing entities within the world (pg. 27-32). Overcoming this perspective and facing up to the meaning of the question of being requires making Dasein transparent in its own inquiry (pg. 27). So I think he is saying more than "we exist."

And the concept that we have to earn being human is so patently false it should be laughed out of any serious (or fallacious) debate that ever occurs

Idk. We do not have to earn being Dasein because that literally happens without our intervention. This is due to the CARE structure of Dasein:

[1] already being-in-the-world --- throwness
[2] being-alongside --- concern --- ready-to-hand --- solicitude
[3] being-ahead-of-itself (in relation to the possibilities of itself) --- authenticity/inauthenticity --- anxiety

What results from this interactive structure—which is better grasped horizontally—is average everydayness; and, it seems, our fallenness. Nothing here is earned. You might be thinking authenticity is earned, because it requires a special sort of comportment to one's own relationship to temporality and one's possibilities. But this is a different claim than one according to which we earn being human (or Dasein). Put differently, what ontologically grounds Dasein is beyond its control.

One reason he is popular is because he attempted a radical shift in ontological investigation, or thinking, or whatever. Taylor Carman is a good place to start if you want to better understand some of his ideas.