I see that you have positive intent, which is why I suggest dialing the perspective. I do not disagree with your points, humans have the power of great destruction. However, if we look at life in terms of balance, then logically, if we are capable of great negative, so too are we capable of great positive.
Let me see if I can walk you through the point I am attempting to make. You stated that you do not believe humans are evolving. While this is an astute observation, it is a message that conveys negative resolution. When we approach a subject in this tone is reflects a finality to our purpose and outcome - it is a finite approach with a futile result.
If we come from the perspective that humans are equally capable of contributing to the world in a positive manner, point out what needs to change, and provide suggestions on how to change it, then it helps abate the negative and opens up the world of possibility - it is infinite, or without end. This allows people to embrace accountability and seek greater awareness on how humans affect other factions of life - animals, ecosystem, and planet.
If you ruminate on my words, I believe you will conclude that a negative approach is essentially coming at an issue from a closed mind perspective. However, if we tackle issues from a positive approach we are effectively opening up people's minds to critical thinking, which brings into the fold hope and change.
So, rather than saying people have grown dumber over the course of the past 200 years, we could say that the evolution of our critical thinking skills have been sidetracked by the concept of greed. Then go on to point out how this distraction has affected the way in which we act towards the concept of life, which affords us the opportunity to suggest corrective actions to better maintain balance of our priorities.
Let me know your thoughts.