I literally said that unless Superman (2025) is bad, I expect it to gross more than FF: First Steps. Superman having more notoriety will probably help the film at the box office since both films are releasing relatively close to one another.You said Superman is more well known to casuals than F4 but he was also more well known than all those other characters. That's not a deciding factor in at the box office.
It's going to mostly be the reviews and which universe do audiences feel more attached to.
Casuals may not even know this a DC reboot and may not give it a chance because they soured on the DCEU.
The MCU is at a low point right now, so the MCU brand isn't nearly as strong as it was during its peak (2014-2019). I expect Superman (2025) to outgross every MCU film of 2025. If not, I would be very surprised.