This is a technical view, not a human-centric view. There is absolutely a level of warnings that will generally work. Not always, but I've found a number of people in the process of being socially engineered trip up on the UAC prompt and become more suspicious, to the point of booting a scammer out of their PC... and calling me. Likely because of the full-screen effect design and the short, but relatively scary language of the prompt.

You've posited effectively that if we cannot stop people from compromising their computer we should not bother to try. Either let them be owned with a trivial popup and a single press, or remove their agency entirely.

However, a better approach to security would be to take responsibility for designs that allow easy compromise, and build systems designed to drastically reduce the likelihood a user compromises their machines.

We can't stop people from finding a shady installer for a driver on a file sharing site hosted in Russia and running it, but we can make 99% of people less likely to do it with good design.