I don't know why it's off-putting that Jerry was always failing at relationships. There's never an insinuation that he's a sexual addict. He just has a ton of first dates because he's a weirdo and so are his friends. It was fairly common for characters in that era of sitcoms to date a stream of new people. The only difference between Jerry and other characters was that the dating was usually a method of creating tension for characters who fans thought SHOULD have been dating. But that type of storytelling requires a sort of earnest humility in the character, and the Jerry Seinfeld character had none to give. Elaine did the exact same sort of thing with men in her relationships.