I don't know if this counts as duming down, but many things I was taught
As a kid, many younger people don't seem to know. Some examples
In a shop recently the assistant said she would need her calculator to work
Out the vat. I told her the vat would be( as I'd worked it out in my head)
She looked at me as if I was Stephen Hawkin
( 10% + 5% + 2.5% = 17.5%, it's very easy, even for Me )
During a recent thunder storm, I was able to tell a few younger friends that the storm
Was 10 miles away, then that it was about 7.5 miles etc.None of them knew about counting seconds, sound travels at around 2.5 seconds a mile. So you can roughly work out
How far away it is and its direction.
Now it's not that I'm smart ( I think I've proven, I'm not over my many posts) but this
Is all basic stuff I remember from school outings and field trips. 
Then again with our crazy health and safety laws, perhaps kids don't get the
Opportunities we older one's did for getting outside. 
"I've been informed that there ARE a couple of QAnon supporters who are fairly regular posters in AJB."