Good point
Hello, Florina and Daniela, I think you are both right. There is a sense that you can, indeed, teach yourself new things, so that your skillset is not fixed in time, like Florina says; but it is also true that, when selling, it is better to have something unique or excellent to sell - hence the specialization, like Daniela says.
Me, I sell my time as a project manager, or as a scholar; but my most important skills are storytelling, divination and forgiveness.