I began reading a design book written in 1995 (31 years ago!) and this quote still rings true:

Design is not something that can be applied after the fact, when the fundamental organization of the product has already been determined – though this is indeed a common misconception. To be effective, design must be an integral part of the product development lifecycle. The process employed by visual designers is comparable to the typical engineering methodology. An initial understanding of the problem based on thorough background research is followed by an iterative cycle of generation and evaluation until the solution that best meets the requirements is selected for production.

— Kevin Mullet & Darrell Sano, Designing Visual Interfaces: Communication Oriented Techniques (SunSoft Press, 1995), p. 7