The use of “complex” in this article roughly means “causing the user to work harder to do things in your product” (search, fill out forms, etc.).
Not what I expected from reading only the title.
This article is about making things easy for the user—specifically making forms valid by default rather than invalid by default, and tolerating a possible increase in incorrect data.
Interesting read, although I think it’s easy to convince readers that “valid by default” generally leads to a smoother user experience, and consequently, I would have preferred a discussion on when or why tolerating incorrect data makes sense and a focus on techniques to reduce incorrect data.