As an experiment, I will concede the language and narrow things to that notion of output.
Coding limits your design because your output will be within the bounds of your development skills.
But this is true if and only if the same person is producing everything, soup to nuts, as in the given example. I don’t think anyone would really challenge that. That was always true in that condition. The best skill in a chain is necessarily the limiting factor.
If the entire conversation assumes the designer is destined to code their own design, then two thoughts: 1) That feels way understated in what I’m reading and 2) Does it even need to be argued that their dev skill is a limitation? Of course it’s a limitation. Where’s the controversy?
But that’s an outlying case today, isn’t it? The argument is in response to the question is “Should designers learn to code?” not “Should designers learn to code their own creations?” The answer to the second question is clear and uncontroversial: Sure, go for it if you want. But be comfortable with your dev skills being a boat anchor on your design visions.
But the conversation has been around designers and coding generally: Should they invest in that skill?
The reason I made the toxin analogy is because the central proposition is presented negatively as a hinderance, not as a healthy additive. A little doesn’t hurt, but beware of dependence. The argument really should be “you don’t have to learn code to be a world class designer” — which for the record is completely true and gets lost in all of this. Knowing code is in no way a requisite to better design. I don’t challenge that at all. That I think is the center of gravity of our agreement.
But the argument, at least the tenor of it, doesn’t seem to stop there. It goes on as if to say “That’s a nice design. It would be a shame if something were to happen to that had you known a bit of front end engineering.” Or worse yet “I personally don’t know how to build out this envisioned feature, so therefore, consciously or not, I’m withholding it from my design.”