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.
I agree that Leia is underutilized in ROTJ (and that the bikini undermines her character) but I don’t think making her a Skywalker is the root of that problem. And retconning Yoda’s line doesn’t undermine all of ESB, it just reorients a one-off line. It’s far more blatant a redirect than anything people claim of TLJ, but it’s still kind of a “who cares” change, it doesn’t matter all that much in the grand scheme of the story.
I think most people’s problem with Leia being the other is more a problem of Leia being Luke’s sister, which serves to shrink the universe and make the love triangle of SW and ESB squicky. I can’t think of anything in TLJ that does anything like that at all.