Consider the intent. Why is this thing made? Who is it made for? Is it accomplishing that purpose?
Consider the circumstances. Is this the right time or place to have this conversation? Will your opinion be valued? Is it your place to give it? Has it even been asked for?
Consider the consequences. Are you really willing to damage that relationship in the long term for the short term “holier than thou” feeling that comes with criticizing?
Consider the other person. I don’t mean to sound elementary, but whatever happened to “treat others the way you’d like to be treated”?
Consider yourself. Maybe you just don’t get it. It may not make sense to you, but it probably does to other people. And those are the people that it’s for. Maybe it’s not for you.
Consider yourself further. Maybe you’re just jealous.
Consider the alternatives. Find something positive. Offer help if it is needed. Ask if they want any feedback. If you’re incapable of doing any of these, then at least have the decency to keep your mouth shut or don’t show up at all.