It's not that none of the writing in these shows isn't bad, or lazy. A lot of it is. A lot of us have expectations that are too high. Game of Thrones had a budget, chache, and scrutiny that gives a reason to expect top-tier writing. Most cartoon shows for kids are extremely low-priority at best from the companies funding them, like bottom of the franchise barrel, and get scraps at best. There's no respect or attention given in it. We are free to complain and we do, but stepping back a second, I have higher expectations for a painter I pay $500 Million to paint a picture and a painter I pay 50 cents, so joke's on me, I guess. With most animation except for Pixar or the most high-profile Disney shit, you need to temper expectations.
In spite of that, in all fictional stories, the bar for redemption will always be much lower for fictional characters. People sympathesize with Macbeth or Hamlet who never would if they were real people. That's the "highest" art there is but still, either their deeds aren't real at all or, depending on how reliable you consider the loose "history" Shakespeare based them on, they're highly fictionalized depictions of reality, so most people don't feel the same way as the would watching a new report about, say, a guy assassinating a political leader, taking his place, and continuing to murder innocent people. Art's whole purpose, or one of its many purposes, arguably is allowing it that distance from reality, otherwise you'd just have news. Thinking about issues from a removed and unemotional perspective because the fiction element removes closeness.
Maybe the Diamonds are evil, but in real life, they could never be forgiven, or even empathesized with, like Macbeth. But in fiction, they can be redeemed, because any blood on their hands isn't real. You can complain about that, but not viewing imaginary people in the same way as real people is just called being a normal person and not insane.