I know that's what you believe, and it's a perception that must change in the tech industry, because it gets in the way of important things like education and it breeds contempt. When you treat people like idiots, they will respond like idiots and learn to hate you because of it.

The "VCR blinking 12:00" problem is a good one, because it is absolutely not caused from a lack of capability. The clock on the VCR is often a very low priority for most people, and while those of us that understand technology think it's a simple thing to set it and move on to other problems, for a lot of people, they estimate that it would require finding the manual, reading it for a while, some trial and error, etc, and they judge it's not worth their time. They have more important things to do. The much easier solution is to either ignore it because they really don't care, or wait until the local nerd stops by and bug them to do it. I would even suggest it's a very good evaluation of opportunity cost.

Now, computer security is very important, but it suffers from a pandemic problem: most people are ignorant (which is not their fault) of just how common security problems are, the cost of failure, and the novel problems that technology has created (e.g. automated attacks that make questions like "am I a target?" irrelevant.

You will never solve those problems by taking people's capabilities away. All you've done is give them a false sense of security, because they trust devices based on an incorrect threat model. Educate them, and they will adjust their behavior. This is significantly less technical than learning how to set a VCR's clock.

As for UI - consider the example I used in another comment: include a hardware switch that must be flipped to allow "sudo"-style access for things like installing software. People understand this (I knew a LOT of non-technical people that regularly used the write-protect switch on 3.5" floppies when they didn't want to erase their homework. Simple metaphors like this, when applied consistently (they shouldn't have to use the switch very often) can help a lot.

You will never solve everything; if you had a truly foolproof way make a safe OS for everybody, I suspect you would have solved the Halting Problem. So use technology to catch the obvious stuff and provide tools for people, educate them well (this will take a few generations), and most people will be safe enough.

What you absolutely shouldn't do is limit everybody in a futile effort to try to make it safe for everybody. This is an impossible task, so you will inevitably end up in a cycle where you remove more and more features, as clever people find ways to abuse them.