You’re asking the wrong question.
“Should designers code?” isn’t a useful discussion.
And frankly, I’m tired of people telling me what my skill set should be. We get it. Designers like to write about and argue about roles, titles, photoshop vs. sketch, and whatnot. I’m no expert on the design industry, but there is one simple thing I’ve found you should be more concerned with:
Find the way you can most effectively contribute to the success of your team.
For some designers, this might mean focusing solely on one aspect of the design process.
For others, it might mean getting wireframes from another designer and then sending pixel perfect PSD or Sketch documents to your developers.
For others, it might mean having familiarity with front-end code, in order to better design with implementation in mind.
For others, it may mean writing some front-end code, to make dedicated developers lives easier.
For others, knowing how to use git and push front-end bug fixes might be important and save hours of back and forth, while leaving your dedicated developers to do more intensive work.
For others, being able to code a concise style guide for you and your developers to use may help everyone move faster.
For others, being able to write production front-end code, and understanding git flow may dramatically increase your company’s development velocity.
At the end of the day, as a designer, developer, project manager, etc, your concern should not be with whether you do THIS, or THAT, or what the meaning of your specific job title is.
Ask yourself, is my current skill set doing the most it can for my team?
Startups are resource constrained. If I can save the company $100k by being able to write production front-end code, I’m probably going to learn how to write production code. If you work at a company that has already raised a gajillion dollars and has a design team of 40, that’s probably not necessary. If you work at a 5 person startup with one dedicated rails engineer, why not learn how rails works so you can understand and modify the codebase? Learning new things does not make you worse as a designer, and in the same way, there’s nothing wrong with focusing on one aspect of design.
Pick and choose what works for your situation. There’s not a right answer. Some dude writing another Medium article on this topic (guilty) doesn’t know what’s best for you. But don’t spend your time trying to pigeonhole an entire industry of people into your preconceived notion of what a ‘designer’ should or shouldn’t be.