Onur Cobanli explains:
You might think that this is a quote about evergreen design you might be wrong. There is always space to improve in design, you can always make something bigger, smaller, faster, stronger, lighter, cheaper. There exists a Pareto better solution that is yet to be discovered, so design never ends. Good design is always incomplete for this reason, because good designer knows where to stop, the point at which it is no longer feasible economically to continue development.