Would you say ROTJ undermined ESB with its retcon of the “there is another” sequel hook?
I would say yes. It’s not really dealt with in a way that is satisfactory or satisfying.
“Leia’s a Skywalker. 'Nuff said.” We don’t get to see her character grow and develop her powers after the revelation that she has some in Empire. We get to see her in a gold bikini and she plays with teddy bears.
I would say that undermines her character and how it was established in Empire and hence the film itself.