Good , usually a word I would use to describe something very ordinary, uninspiring and something I would soon forget.
It is one of the least enthusiastic positive ways of describing something.
Thinking back to primary school 'good' could always be related to 7/10, whereas a higher mark, for example 9/10 would be described as 'excellent'. I have always thought of 'good' as just above average.
If I were to describe a design as good, it would be something I would perceive as uninspiring and mundane.