I’m not much of a word stickler, but I do object to people confusing the word “simple” with the word “simplistic.”
“Simple” means, well, simple: uncomplicated, straightforward, easy to understand.
A simple design is clean, but it can also be clever. Sometimes a simple solution takes a whole lot more thought than a complicated one.
“Simplistic,” in contrast, is oversimplified, dumbed-down, and probably stupid from the get-go, like the idea that building a wall on the Southern border will solve the immigration problem.