@World in Scarlet is right. Kurt is by definition is an involuntary celibate as far as all evidence points to as in we have never gotten any indication that Kurt is having any sort of casual relationship while he openly professes he cant get a serious one. I don't think Kurt fits neatly into the public conception of an incel but really it seems a bit petty. I didn't get jealousy or rage vibes from his whores segment on initial impressions but I wasn't reading into it much on this I don't think World in Scarlet has it correct and it seems to be the main point of contention. How much does it really matter though?
Kurt is one of the few people in his type of situation who actively tries to better himself which is endearing, but a spade is a spade.