Just in terms of healing I think it was a missed opportunity for both Princes but especially Harry being younger with a more pronounced trauma overall to deal with than others. He has spoken of being in less than a great way for a considerable time. When realizing and discussing the problem with his brother back then, William recommended he seek professional therapy for it.
Therapists are helpful, but you can't buy what Paul would have given, not only relating to the loss, but intuitively feel the pain on many levels. And since he was a basket case himself, both would surely have improved over a period of several months, or perhaps years. Even today they would benefit by getting together or talking once in a while.
Harry would shock the monarchy and nation to the core if he ever did that.