By definition, criticism cannot be constructive when its motivated by disappointment. Three “nevers” can guide you: Never object to mistakes you knew about before hand, but waited until after failure to care about. Never offer a critique without focusing on a clear and helpful path forward. Never used the phrase “that’s on you”.
If you can’t say anything good, don’t say anything at all. When you point the finger, at least three of your own point straight back at you. We all have plenty of blame to go around. That’s why leaders with winning teams find only solutions, never blame.