People are bringing up characters like Goku, All Might, One Punch Man.
One Punch Man is is a deconstruction of the superhero genre. He's also nothing like Superman.
All Might is not the main character of My Hero. He's the mentor like Gandalf or Dumbledore. The world and the stories don't revolve around him.
Goku has become a perfect example of how not to write a character like Superman. He's a main character who has had 0 character development in decades across several hundred episodes. He's become the least interesting character in his franchise even as he pushes other, better characters aside. He's an idiot who faces no consequences for his mistakes and his neglect of his friends and family is treated as either a joke or the right decision. The story even moved past him over 25 years ago and he's only the main character now because of Akira Toriyama's inability to write other characters with more depth or to tell stories outside of a very specific and extremely limited range.
The Goku problem is not unique. Amine is full of examples. Ichigo in Bleach became one of the least interesting characters in the show after the first major arc was completed. Sailor Moon is by far the least interesting character on her team. There is a real problem with main characters becoming overpowered and bland in long-running franchises like these.
I don't think Superman suffers from that problem, at least not to the same extent. But I think he does suffer from 'Seinfeld is unfunny.' As the first and archetypal superhero, Superman inspired pretty much everything else. So when they want to change directions with him, someone's always going to compare it to what was done with another character. Trying to give him relatable issues led to accusations of 'Marvelization' even though the rest of DC was moving in the same direction at the time. Man of Steel was accused of just aping The Dark Knight because it tried to be darker and more philosophical even though its story about an outsider struggling to fit in was not a story that can be told with Batman.
Is Superman harder to write than Batman? I'd say categorically and unequivocally yes for several reasons, including those listed above. You can't have threats on Superman's level all the time or they lose all impact. Nor should Superman be saving the world every other month without it losing all meaning. That human aspect is needed just as much as the larger than life aspect. But if the Wonder Woman and Shazam movies can be as good as they are then I don't see a reason why Superman can't have the same quality.