I know people with PHD's who can run rings around you on "their topic" and can't cross the street without support.
I know teachers who are smart, and phenomenal at their job who I had to arm twist to go play with chat GPT cause it's not in their wheelhouse/on their radar.
The not so bright person, who is stressed out is likely a user of your app. The same as the absent minded PHD or the teacher who is too over worked to care about your new tech widget.
These are real people. And there are a LOT OF THEM (for there to be an average 100 intelligence there are a fair number of people UNDER IT). You can go look on FB/YouTube/Ticktok and find them. "Stupid" people exist, there are a lot of them. Making sure your app works for them is good for them, for your company, for your customer support costs... The whole point of usability is to get average, less technical people in and get them testing your app.
To put a fine and final point on it, after 90 IQ, the author went on to talk about blind people. Candidly your app working for everyone with a disadvantage is just good business and shows a LOT Of empathy. A point you seem to have missed in your indignation.
