One of my high school teachers said something like: if someone doesn't understand your explanation, then you don't know it as well as you think you do.
Why?
First, because far more things can be explained to an intelligent lay person than most of us realize, and figuring out how to do so improves our own understanding. Therefore it is worthwhile to make the attempt.
Second, because it is far too easy to fool ourselves into thinking that we're making a succinct explanation that requires domain knowledge when actually we're spouting just enough jargon to remind those who agree with us of shared and possibly unexamined dogma. There is a real cost to mental habits that make such mental mistakes easier to make and sustain.
So yes. The other person may be too ignorant/stupid/whatever to understand you. But the alternative explanations should be disproven before you conclude that.
if someone doesn't understand your explanation, it might be that you don't understand the person well enough or you don't know the correct way to explain to that person in a plain language
My answer always changes since I haven't narrowed down a way to describe "cloud engineering" to people.
I've heard this saying before and every time I think, "maybe I don't know what I do".