I don't think this has anything to do with design tbh. You have developers who are comfortable with HTML/CSS/JS and those who prefer to stay clear of it. A lot

I don't think this has anything to do with design tbh. You have developers who are comfortable with HTML/CSS/JS and those who prefer to stay clear of it. A lot of those HTML/CSS/JS folks happen to also really enjoy (and are great at) PHP/Ruby/Python etc - not so unicorn-y