You don't fully understand a design idea until you think through the scenarios where it will fail.

All designs fail. In an infinite number of ways.

What we call "good design" is largely about matching the designed thing with the right people, right scenario and right timing.

Change one of those and a seemingly great design often falls apart.

When someone says "I LOVE this design, you should get it!"

They're rarely thinking about your needs, your scenario and your timing. Or anyone else's. Bad product reviewers do this often.

Good design is conditional "If you are X, and need Y for Z at cost K... it's good for you"