Even when criticism is invited or asked for, the person may not be ready for the truth. If we offer it, we might find an unpleasant reaction. Sometimes criticism, when solicited and when given with care and honesty, can help someone see and understand something about themselves they otherwise would not have known. It often gets to the intention of the person giving the criticism and how it is delivered - the tone of voice, what terms it is couched in. Better to not say anything than say something critical.
Silence can be golden.
Of course, you don't want your silence to be interpreted as criticism. Look for ways to help make the decision work. Find something sincerely positive about what the person did. Instead, listen, show empathy and don't judge.