From Simon Willison, in a post about Margaret-Anne Storey’s concept of cognitive debt:

I no longer have a firm mental model of what they can do and how they work, which means each additional feature becomes harder to reason about, eventually leading me to lose the ability to make confident decisions about where to go next.

This is a similar problem to one that I’m dealing with in a large legacy system at work: the people who designed the system are no longer around, and many of the decisions made in the interim have been bottom-up solutions to transient problems, rather than cohesive approaches working with the grain of the application.

I suspect that the advent of LLMs for programming is not going to resolve the issue.