Ringnecks are generalists and will eat pretty much anything, i'm not sure on their ability to digest crickets as it probably hasn't been studied since they've never been popular among people or the pet trade. So I wouldn't say they can't, but I will say a varied diet is better and an only cricket diet most likely isn't healthy and will lead to problems. They are often found in groups in the wild despite the fact they have been known to prey on smaller snakes.