Thoughts on why Keilson's Holocaust novel has not been recognized as a classic

Why isn't Hans Keilson's "The Death of the Adversary" a recognized classic? Well, I'll hold off my own judgment till I finish, but half-way through it seems like a grossly unrecognized novel, rescued from oblivion by an FSG reprint (and a NYTBR cover review) last year. Still - why isn't Keilson ranked (and read) along with Levi, Wiesel, Ann Frank, and other Holocaust survivors and chroniclers? Probably because his tale is both less horrifying and less reassuring than others'. His is of a young man who resists the resistance, refuses to acknowledge or recognize the danger of Hitler and the Nazis, refuses even to name Hitler, refuses even to identify himself as a Jew. We don't get the heroic and tragic resistance and (ultimate) survival of a Wieself or a Levi, we don't see that plaintive suffering of an Anne Frank, we don't see the valiant struggles of a young man as in Koszinski or Begley, we don't even get the rueful and ironic resonance of a story such as the recently discovered Suite Francaise, in which part of the haunting aspect of the (unfinished) novel is knowing of the author's fate (death in a camp). The closest kin may be Fallada's novel, also recently rediscovered, about ineffectual German resistance to the Nazis. Keilson's is darker and less appealing, much more of an intellectual's struggle, harder to identify with, told in a way that Kafka might recount the Holocaust had he lived through it - full of weird abstractions and refusals to act rather than heroic action or tragic resistance.