That's a fair point, but Clark's appeal has never been in being the "not gritty one" and the success of the MCU is only a good thing for all of us. If a film is quality, he doesn't have to worry about the competition any more than Aquaman did.
I suppose it's true that the MCU has pushed fans of the genre out of the "grimdark" stuff, but plenty of things still revolve around that hook. People were talking about Game of Thrones earlier and you don't get much more grimdark and twisted than that. Breaking Bad, Lost....all the shows in recent memory that have dominated the pop culture discussion have been pretty serious and screwed up. The MCU is kind of an outlier in this, and some of their films haven't just been zingers and action set pieces either.
I definitely agree with the idea of giving Superman back to kids. That's who he belongs to, not old bastards like me.
Smashes the Klan seems like a good place to start. Done right, that's the kind of movie that would make Into the Spider-Verse seem like a modest success.