1. Aside from Wonder Woman, he didn't have much competition in-universe and was still the mightiest. The Silver Age eclipsed that take in terms of iconography anyway, so there is no point in adhering to it. Even scales down modern takes lean more towards the Silver Age than earlier. For example, he's never stopped flying.
2. I'm sorry, but if the other characters need for Superman to take some hits to appear useful...than they're not that good to begin with. And if a writer can't write all these icons at peak efficiency while providing credible threats for all of them, they have no business writing JL.
3. Appealing to that crowd isn't worth it. They're still not gonna read Superman. And it's telling that he's trailed behind Batman in terms of popularity ever since Crisis powered him down and gutted his mythos