Site performance is potentially the most important metric. The better the performance, the better chance that users stay on a page, read content, make purchases, or just about whatever they need to do. A 2017 study by Akamai says as much when it found that even a 100ms delay in page load can decrease conversions by 7% and lose 1% of their sales for every 100ms it takes for their site to load which, at the time of the study, was equivalent to $1.6 billion if the site slowed down by just one second.
Engineers seem to have a clear, if usually implicit, model of the process of design. It is usually an orderly model of an orderly process as the engineer conceives it.
The notion that the design process should be modeled as a systematic step-by-step process seems to have first developed in the German mechanical engineering community.
Herbert Simon independently argues for design as a search process in The Sciences of the Artificial. He was motivated to lay out a strictly rational model of design precisely because such a model was a necessary precursor to automating design. His model remains influential even if today we recognize the "wicked problem" of original design as one of the least promising candidates for AI.
In software engineering, Winston Royce independently introduced a seven-step Waterfall Model to bring order to the process. In fact, Royce introduced his waterfall as a straw man that he then argued against, but many people have cited and followed the straw man rather than his more sophisticated models. Even if ironically, Royce's seven-step model must be considered one of the foundational statements of the Rational Model of Design.