Yes. It's correct

If you just say "I haven't had lunch", then it's possible that you won't eat lunch at all today. Maybe you are fasting or dieting or just not hungry. But if you say "I haven't had lunch yet", then it is clear that you plan to eat lunch later. So for instance, if you say "I haven't visited the Moon yet", this would be a very surprising sentence because it means you think that you will visit the Moon some time in the future.

Yet means that something has not happened up to this moment but you expect it will in the future . I have not had lunch yet .... means you did not eat lunch today, but you are going to, perhaps sometime soon.