or too under-powered in relation to the powerful organizations that take advantage of them, or too overworked by all the tasks and details of their lives to deal adequately with all the things it might be beneficial for them to deal with, but are not strictly necessary for getting through the day.

No. It is so that they don't have deal with developers tricks and misdirections and intentionally misleading uis and so on. It is also so that they are not required to learn tons of obscure and otherwise useless knowledge to function reasonably.

None of that makes them stupid. Just like, when I am in grocery store I can be sure all food there is reasonably safe, even if I don't know anything about them. I am not expected to research them all personally for dangerous substances else "I am stupid for poisoning myself".

When talking about UX, there's this bad habit of using people's mothers or grandmothers as examples, because they are 'too stupid' to understand the UI that was built. Aside from the obvious problems, this also implicitly removes blame from the designer/implementor of the interface.

I always prefer to reframe it as someone with a very important, intelligence requiring job, say vaccine reasearcher, who doesn't have time to deal with your shitty UI when they want to print a document.

I feel the same applies here.

no. They just can't care about everything themselves individually all the time.

So penalising unwanted behaviour isn't about stupidity at all.