I don't understand your metaphor.
> E2E can be explained to an 8 year old.
Can.
Also, the main problem here isn't explaining the tech itself (although the quotations in the link indicate this is also a problem), but rather explaining why it's (a) actually good, and (b) impossible to prevent even if it wasn't good.
But even if it was the tech itself, most people don't have maths skills and fundamentally don't (care to?) think logically.
When I was a kid, I couldn't understand why the adults kept joking about why it was so hard to stop the VCR from flashing 12:00 when I found it trivial.
(I think we're getting to the point where you could run an image detection process on the display itself, totally circumventing any encryption. This will have a lot of consequences that are totally obvious and yet it may be done regardless).