No, that's too easy a way out. We need to face up to the fact that the Iraq War was a failure of our overall political class and supported at first by a strong majority of voters.
That's rather like letting identified murderers in a pogrom walk free because they had a mob on their side.
Holding individuals to account is valuable even in the absence of (more important) systemic change. The justice is an end in itself, but it can also create a culture of fear amongst those closest to the convicted. If it can happen to the President, it can happen to the Secretary of State (and so on).