Like I said, who you going to put out there for 20 minutes as the 4th guard? If there are no other viable option to fill in that 20 minutes, the alternative of sticking someone like Guy or Ramsey (who are not ready for PT) would make the Kings worse than CoJo does.
TBH, you guys make it out like he has Chris Paul, Lou Williams or Fred Van Fleet sitting at the end of the bench waiting to relieve Fox when he needs a breather.
I don't get to watch games, so will not hazard a comment on the actual play. However if +/- is any indication (I know it's often flawed, but given our relatively tight rotations, perhaps not so much), CoJo has been quite bad. Here are his numbers for the last few games
Clips: -6
Nuggets: +1
Celtics: -2
Pelicans: -5
Heat: -11 (He also went 0-4, had 1 assist and 2 turnovers in a game we lost by 1 point)
Raptors: -10 (though he did have an excellent shooting game here)
Magic: +1 (In a game we won by 14 points)
For the season, he's averaging 5.9 points, 2.1 rebounds, 2.3 assists and 1.1 turnovers, while shooting 42.2% overall and 30.2% from 3. These are fairly pedestrian numbers. He might still be better than Guy, but at some point, we need to see that given consistent minutes, can he do better than CoJo?