When you stop to think that everything, I mean EVERYTHING in the world is designed, the world of design starts to take on a whole new importance.
Design is about asking "why", at every stage. This is to make sure the purpose or function is the primary focus, not just the "pretty" parts.
Good design is practical, elegant, and often, seems very, very simple.
Bad design does not serve the purpose for which it was "designed." It lacks elegance. It is often clumsy. It is a waste of time and energy.
Mediocre design often makes no impression at all - so for the most part, I consider it quite useless. This would be something that works, but not well. Or it is so short-lived that it feels like a waste of human potential.
Quite simply, good design is important because it makes our lives and our world more beautiful, simplier or easier. Often it does all three at the same time.
One thing that I am increasingly noticing is that we don't question design enough. We let the status quo direct things. I think we need to look at things that we have been overlooking for some time and ask if it is a truly useful, practical, elegant and appropriate solution to the need at hand.