The difference between expert and advanced/intermediate technical staff is that the advanced engineer has an understanding of complex solution and mistakenly tries to apply them everywhere, so the net effect is to increase complexity. The expert typically sees simple solutions and method of resolving complexity and has a net effect of reducing overall system complexity.
Believing that the value add of experienced technical staff is to only solve really hard problem is likely caused by having too many advanced/intermediate people playing the role of experienced technical leads. All of the great technical team member I worked with always make call solutions simpler and easier to implement by knowing exactly what doesn't need to be done and what is essential.