I think a lot of these boys survived on pure natural talent, then minor niggles, lose 1% of speed or teams study some tape. These help to negate what makes them good.
Again just my opinion but a lot of them never had the work ethic or the desire to work in face of adversity. We've had so many of these players and unless they go early to other clubs (paps, Katoa) then they don't grow. This is a fault of our pathways until now I think.
Fus, Konny, Ken, Kata I feel all fell in this category. I am sure there are more, but after working this, these 4 players are all in the same kind of era, so maybe it is the coaching/management?
Anyways, hope Ken goes well.