When Youngs first broke out on the scene, his ability to spot a gap was second only to Genia. He darted round the fringes frequently and the pace he put on the England game was fantastic. Care's problem around that time was that his passing/delivery was slow, and it suffocated England's ability to play flowing rugby.
A few years later, and it's like Care and Youngs have traded places. Youngs barely ever looks to run and he's slow to deliver the ball when playing for England, and his box kicking is frequent and mostly too long. England's attacks flow with Care at the helm, they do not with Youngs. This is why Youngs is a liability. It isn't necessarily that he's an obvious liability in that he makes many blunders in a game, it's that England struggle to build any kind of momentum in attack with Youngs guiding them from 9.
This is why I prefer Dickson to Youngs in general: Dickson doesn't do much flash, but he's got a decent pass. If that means that the 6 other backs in the backline can play better, then so be it.