It is very rarely productive to adopt an “either-or” stance in UX, or in any other human endeavor for that matter. The UX discipline, with its many layered and intersecting tactics and methods, is much too complex for a simplistic black-and-white outlook. Often, things that are rejected as a result of developments in the field are not necessarily suddenly useless, but simply used the wrong way.
Such is the case of the much-reviled mock-up.
Today, this particular deliverable is often seen as an obsolete component of an antiquated approach to UX. And for a good reason – the mock-up is simply not a very useful development tool. In-browser prototyping generally represents a more practical approach, since it presents a continuous path from wireframing to final design, allows designs to adjust dynamically to shifting viewport widths, and also offers a more accurate predictive rendering of the final product. The work involved in keeping a mock-up updated and accurate through the development process, while at the same time offering an adequate approximation of the end result, as well as reflecting the many different possible page appearances in different browsers and viewports, quickly makes static mock-ups a costly and time-consuming proposition.
However, as a sales tool (as opposed to a development tool), and a relatively nimble way to deliver a quick approximate snapshot of the stylistic design intent, the mock-up still has a purpose. Given the time required to get a prototype to the same spit-and-polish as a mock-up, and given that this level of design detail and fidelity is often attained closer to launch (which is much too late to solicit constructive input from a client), a mocked-up page used the right way can facilitate an engaged look-and-feel dialogue with clients. The mock-up should really be seen as a rough, early view of a design inbetween a wireframe layout, and a finalized, fully styled page. Other forms of design deliverables, such as so-called style tiles, or moodboards, lack the applied visual structure of a laid out page, or the coherence of a properly defined visual hierarchy and integrated design system, that is typically evident in a mock-up.
As long as recipients of webpage mock-ups are aware that they are looking at an approximation, the sense of design progress that a mock-up represents often yields early insights into the client’s brand experience requirements, buys a team more time to get it right, and polish the end result. The pitfall of the design process is when the mock-up becomes a pointlessly iterative development substitute rather than a one-time conceptual presentation element, but this is easily avoided if the presentation of mock-ups is properly framed at the outset.
As is often the case, in UX and elsewhere, evolution is preferable to revolution. A revisionist approach to UX, where dogmatic, tendentious design and tool choices restrain the process for no identifiable reason or practical gain, has few real advantages over a more pragmatic stance.