If JCH is 26 then he's fully developed. If he's still banging around L1 then he may surprise us all and be the black swan in a higher league, but the odds of that are ... well ... low. And, we're a white swan Club, we don't need black swans, black sheep ... an unfortunate use of color adjective predominate.
Cullen, Whittaker et al are ours for better or worse and if we don't believe in them and they don't have the technical ability then why were they acquired and still on our books. The crux of the matter is technical ability and a head for the role ... you can't put that in, it's either there or it isn't ... but you can get them wiser and bigger and that's where game time comes in.