I would really extend this to the following qualities that people in the field of building products should try, to the best of their abilities, to be good at. They might not become the best at each one, but enough to become potent and in the very least better than they were before trying:

-Understand technology. What it takes to build, scale, maintain and fix things. What are the affordances and benefits of one approach over the other.

-Understand design. Not just pretty pixels (in fact that is the least important part, IMHO). But the WHY. How it affects people, what the goals are, why the current system is broken or why it does not exist.

- Understand Marketing. How do you convince others that your product (idea or finished) is THE one they should vouch for. Why should they invest time and money into it. How can you make them believe that you know what you are doing and better than any bad experiences they have had with products of that kind. Selling/Marketing is not evil. It is a necessary (evil). Many humble and smart people fail to understand that.

I totally understand it is very hard for one person to be great or even good at all three. But hey most don't even try, so you are already better then them the first day you try.