If we were gods that had an absolute view of all things then I would agree. But the world is not so convenient. There is no higher being, no witch, no author, to present us with red. Even people who have been “proven” to be guilty in a court of law can later be found to be innocent. However in the time in between the “truth” that society believes is that they are guilty. Some people who are close to them may hold on to a personal “golden truth” in their innocence.
The message at the end of Umineko is to find your own golden truth. Reality doesn’t have a nice answer that a higher being can simply hand to you, and so neither does Umineko. You must find that truth on your own.
That’s an extremely black and white way to view it. A good person can still do a horrible thing. As and often unforgivable a crime as murder is, a person is not defined by a single act, a single day of their lives. Good people can commit evil acts. Umineko is not a story about making a criminal pay for their sins, but understanding the tragedy that led to an even greater tragedy. It’s not a story about finger pointing but about humanity.
The point was that finding the truth is only one way of moving on from a tragedy. Ange’s journey was a journey of grief. She passed through all of the classical stages of Grief.
Denial - she believed her family could return home to her, that Battler could defeat the witch and give her a happy ending.
Anger - she lashes out against Eva, accuses and blames her.
Bargaining - she searches for the “truth” but really is just looking for someone to blame.
Depression - she realizes that no one is returning home, that the truth is not some convenient thing that can make her pain go away.
Acceptance - She finds comfort in remembering that her family loved her, in believing that they were fundamentally good people, and that they are watching over her and wishing for her happiness.
The point at the end was that searching for a truth she would never find would not make her happy. The point was to live for the future instead of being trapped in the past. The point for us viewers was to not just view a mystery as a puzzle to be solved, but also as a story about people with goals and ambitions, hopes and dreams, pain and suffering, joy and happiness. The game of a mystery is fun and enjoyable, but just like anything else the true value lies in the journey itself, not the destination.