yes, but then you end up with a bunch of unrelatable syfy illnesses that serve the same purpose. And that comes at a cost, I can't relate to a character dying of martian barnacle poisoning the same way you can to a character suffering from cancer.
I'm also on the controversial mindset that Superman shouldn't step in on these types of things. Take potential accomplishments like curing cancer away from humanity. He should be a protector and role model to humanity, not make them overly dependent on him. Let them make their own milestones.
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He starts curing cancer, aids, refreeze the ice caps,give humans flying cars with cold fusion, then that's great. But he'd be proving that Lex Luthor was right all along.
On the flipside, it might make an interesting story where he does cure AIDs, but then wrestles with what to do with it. Maybe he'd actually give it to Lex, so he could take credit for it, but then Lex weaponizes it and boom, there's the story.