No, he is often a liability, makes too many goal conceding mistakes.
Yes he has the odd good game and occasionally does something good with the ball. By his standards he is having a decent season.
He certainly gets blamed for many goals, unfairly so. Plenty on here blamed him for Konsa's red card v Newcastle for example! It's called a scapegoat. Goal conceding mistakes are rarely the fault of Cash or Digne to be fair to them. The preserve of our higher rated keeper and three regular centre backs usually.
Ned, Garcia, Konsa, Disasi - all given chances at RB to replace him but he has seen them all off. Sign of a very solid character - same for likes of McGinn and Watkins. Plenty doubt them and they kick on again.