You could look at his time at Palace and say that he's the DOF that oversaw them rising to their peak, and winning the FA Cup which is a pretty impressive achievement for them, recruiting players we'd have loved to get here (Guehi, Wharton, Olise, Eze (booooo!)).
On the flipside, I'm not 100% certain his time overlapped with all of those signings, and even if it did then it's still not any guarantee that he's particularly responsible. We could bring him here and find that the secret to that success was just a decent scout in his team.
Either way, he can't be as useless as this twerp: