Over-optimization
Proper Optimization is very much concerned with finding the right balance of optimization. This means that being overly concerned with optimization and insufficiently concerned with optimization both have costs. Optimization is about maximizing a value, and thus the term over-optimization is in a sense meaningless. Over-optimization is sub-optimization.
Generally, I prefer to use the term over-engineered to describe this type of over-concern with optimization, as I believe that better respects the idea of optimization itself. This way we can differentiate between being overly-concerned with creating a perfect structure (over-engineering) and arguing for the existence of a higher maximization possibility, i.e. arguing that the status quo is sub-optimal.