By Star Trek standards, the amount of "bad writing" on this show has been...virtually nonexistent. By comparison with all previous series and movies.
But as has already been said, "bad writing" and its idiot cousin "lazy writing" is just code for "I don't like this."
Well, who DOES like bad writing?
I think some people feel personally attacked when you say something they like is written poorly. I can only repeat that you could keep all the things you like about La'an and Una and still tighten up their stories, make them less similar, and find a better justification for La'an being Khan's descendant. I still maintain that they WILL ultimately exploit this feature of La'an-- there is no sensible reason not to go there. I just think that eugenics prejudice would have fit her like a glove, and that a separate kind of drama should have been reserved for Una.