I agree with you mostly, but that applied to how web tech were developed in the past. Now you have CSS 3 doing animations, adjusting to viewport for content to be prioritised. HTML 5 and all their attributes which all affects things such as prioritising asset loading and stuff. The gab between UI/UX and backend is getting thin by the day. Javacript and UI/UX are used together for the "mordern UI/UX". The web specifications are getting complex and confusing by the day. Node JS, SPAs, RWD, React, angular, etc all makes sticking to pure SoC difficult. As of 2016, you really need to learn JS as a frontend dev because the gab is getting thin with the direction the web is going.