“Complex” is not the antonym for “simple.” Something that is complex can be simply complex or confoundingly complex.
For instance, a group of related buildings is frequently called a complex. We know that complex can be a pleasingly arranged set of units with straightforward passage among the units. This would be further simplified by having a logical functional arrangement of the departments within those buildings and the complex. Parking for visitors would not be widely separated from the most visited office. The executive offices would be contiguous, not spread, willy nilly, throughout the structures.
Use the words, “confounded,” “garbled,” or “messed-up,” when that is what you mean. Use “complex” in a simply, orderly way.
— Kilgore Forelle