Why should we solve hard problems? What is in it that an easy or a medium problem does not have?

What is Characteristics of Difficult Problems? Please add your thoughts.
This is what I could find from the internet. They are as follows:

1. • Intransparency (lack of clarity of the situation)
   o commencement opacity
   o continuation opacity
2. • Polytely (multiple goals)
   o inexpressiveness
   o opposition
   o transience
3. • Complexity (large numbers of items, interrelations and decisions)
   o enumerability
   o connectivity (hierarchy relation, communication relation, allocation relation)
   o heterogeneity
4. • Dynamics (time considerations)
   o temporal constraints
   o temporal sensitivity
   o phase effects
   o dynamic unpredictability

The resolution of difficult problems requires a direct attack on each of these characteristics that are encountered.
In my opinion, hard problem requires one to have higher order skills from these triangles.

pic. credit: https://i.pinimg.com/564x/2d/57/84/2d5784ef6e4604d8cf91bb280e91008d.jpg