Self contradiction is the form least likely to be noticed since the conversation needs to include multiple stories for it to be noticeable, but it definitely happens. Just off the top of my head, the Last Jedi backlash included at least a few people that I saw arguing that Rey was a terrible character/mary sue for having certain character traits while claiming that Luke was ruined by not having them. I do agree Marvel's success is something to aspire to, and maybe your Klingon example would have been a step in the right direction - I certainly wouldn't have minded. But the focus on visual coherence with a pre-established legacy is not really supported by Marvel's example. They've made tons of visual updates, many just as drastic as the dsc Klingons. Maybe it's just a question of knowing what you can change and what you can't, or of Marvel's pre-existing fanbase being smaller. Maybe it's more complicated than that. It's hard to say why marvel gets away with so much, just that they do. Sure. But clear, indisputable consensus has always been rare. In examples a few tiers lower than Empire, the consensus is harder to pin down (I'm not at all certain the consensus on ds9 is as good as you think, much as I love it). And the internet's constant distortions make it much harder than it used to be, too.