Not so: people hate it because it goes meta (to a greater extent than most of the other episodes), because it retreats into allegory and humour and fourth-wall-breaking rather than providing a clever resolution on the spy-fiction level; but everything in it makes sense. McGoohan, evidently, had a Catholic attitude of fundamental pessimism about the human condition. He believed that the root problem with human society was human nature, and he didn't share a Randian belief that autarkic superman individualists were blameless, or a Star Trek utopian-socialist belief that the future would raise up a New Man to sort everything out, or a conviction that everything will be groovy once the Revolution comes. Given that, there's basically no one else that Number 1 could be (notice that Pris. doesn't look very surprised to find out), and no other way the series could end (nothing changes, basically).