I don't disagree with you. However, you are ignoring one key point that I made: the difference of base intelligence.

Let's assume you have an IQ of 135. You are not that far from even the crazy smarts at 150 and as long as they have some social skills, it will work out. I, myself, never had issue with understanding the smart people.

Now let's assume you have an IQ of 110. Unless 140/150 IQ people are spending inordinate amount of time formulating how to simplify things for you, things will fly above your head.

This does not mean just because someone is 150, and someone is 110, the 110 is always the problem.

This also does not mean an 120 explaining something to 140, and failing is 120's fault or the other ones'.

Every combination is possible as we are talking about personalities/ability to articulate oneself.

However, I was talking about a specific scenario, which I have faced myself and saw it happen a lot of times (to other people), where someone's simplification level is still higher than someone's max understanding level simply because the deviation between their caliber is too great. In most cases, this can be worked around by the explainer spending inordinate amount of time.