Offline I do not have a problem with Superman matchup as I can react most of his "zoning" tools. If he MB laser sweep its a victory for you, just gotta train yourself to block low high at max range always. I can only speak from my MU which is Flash and I feel it is 5/5 at worst possibly still plus for Superman. Unfortunately there are a few players I hadn't gotten to play yet with their best supermen, but I sincerely feel that it is not a terrible match. At max range, sure I may have to think and react better than Super man, but if you take that part of his game away Superman really cannot handle flash mid or close range. I started learning this game a month + after game was released and had to learn to play against superman for the majority of my playtime and initially I thought it was stupid and impossible.
Now though I really believe the match up sucks for superman. Again I am not experienced enough with other characters to even attempt to justify whether supes should be nerfed or not, but there are clear universal tools that can be used against superman.
1. Air dash/ air mobility seems very strong against his full screen stuff.
2. Ducking and dashing. Blocking and dashing. Neutral jump or foward jump. Use a combination that works best for your character.
3. Trading projectiles with laser sweep is typically a win for you.
4. Really just training mode superman on repeat to see the different tell he gives for sweep and shot until you can make a read on it.
5. Stage select matters, please explore this more. Even if you are both power characters there are better stages against Superman and worse ones.
This is just the anti zone stuff. His strongest game is midrange as stated before, but I have found with 5 characters just training mode for a little bit they have meterless options to contest his string. (most are hitbox related seemingly) Also universal ways to deal with it with meter. I am not trying to say Superman is bottom tier, but I feel there is a character that already in my eyes is much better than superman. Also, there are very few characters that I would rank below the rest of the group with my current matchup knowledge.
Sorry I know people dont like to read here so
Superman is not a problem right now.