Everyone knows who the Fantastic Four are.
If Reed Richards blows up a city block, people know who he is and can hold him accountable.
Also, for the most part, the FF deal strictly in major earth shattering events like mole man invasions and Skrull infiltration. They leave the street level shit alone and let the police do what they're trained to do, which Jonah appreciates.
That's not to say the FF will leave crime alone if they see it. Sue would probably stop a bank robbery if she happened to pass one while out with the kids. Johnny would stop a car jacking if he happened to fly by because it looks good. Reed would probably go out of his way to get a cat out of a tree for an old lady with his freaky stretching arms. But none of them actively go out and seek it like Spider-Man does.
The only FF member I can see actively searching out street level crime to thwart is Ben, and that's because the street is something he understands, and smacking down some gang banger gutter trash ruining other people's day seems like something Ben would do to relieve some stress in his shitty rock man life. But Jonah won't call him on that, because the man was an astronaut, and Jonah has a massive respect hard-on for them and every other profession you'd find in the classic G.I. Joe lineup.