The "lost art of software design" refers to the idea that the principles and practices of software design are not given the attention and importance they deserve in the software development process. This can result in poorly designed systems that are inflexible, difficult to maintain, and prone to errors and bugs.
There Are a Number of Factors That May Contribute to the "Lost Art" of Software Design
Time Pressures
In many cases, software developers are under pressure to deliver new features and functionality as quickly as possible. Unfortunately, this can lead to a focus on speed and efficiency at the expense of design quality.