You need a break from super heroes of like 10 years, like in the 1950’s during the Wertham crisis. Then people have to come up with something different in a vacuum.
As it is today, creating a new character in a landscape filled with similar themes makes it too difficult to come up with something unique, because it reminds you of one of the icons who already exist.
I think your next iconic hero comes from a similar layoff period as the Wertham era. Like some crash, or world war, and you have to be encouraged by someone who comes out of that crisis. Generally, a really big iconic hero emerges in a landscape of chaos/crisis, like it was in the 1930’s where Democracy was under threat in the US by fascists and communist voices everywhere. Capitalism failed because of the 1929 crash, so Americans were toying with other creeds. You had to get the country back on track, and to do that you had to get iconic figures that resonated with the people.
Superman was the first icon because people felt powerless to do anything in the 1930’s. Superman came along like a breath of fresh air, because there was the answer, all in one package. How to help people, rescue people who were feeling paralysed, by doing good acts, because Superman was powerful. Bullets couldn’t hurt him, he could fly, but most of all he was inclined to save the helpless. That triggered something in the human spirit that needed that kick of inspiration that was holy. Goodness.