[illwrks]

You need to clarify what you understand "design" to mean.

There is "design" which is to make something pretty and aligned to the latest trends. (Junk design IMO). You'll largely need some experience with design tools and frameworks to make things look good.

Then there is "design" which is more about the experience of something, how information is ordered and how usable something is for your customers. This is one hundred times more valuable and you probably need more usability, user experience and "design thinking" experience. You likely don't need to learn any visual design tools but you can easily pick apart your application and understand "what does the user need to do now".