> I agree, but are HR people agreeing on this?

Really depends on the company I guess

> Is it sufficient to be skilled in one programming language, such as Python, and implementing a software renderer or ray tracer, your own neural network, your own HTTPS server, your own OS, your own memory allocator, your own interpreter, your own virtual machine...?

May be misunderstanding here, but if I was implementing my own OS I probably wouldn't be using Python. Different problems warrant different solutions – by a "general problem solver" I mean that you think about the coding language as a tool to solve a problem. Similar to how you might think of S3 or ECS as a tool.

That you're thinking of the problem in the business context rather than purely the technical context.