I didn’t watch the video, it’s too long. I have a couple of thoughts though.
You say that some things are better than others for people, and I agree, which leads me to believe that there are optimal behaviors for human happiness and flourishing, at least for people interacting with each other. That implies objective morality.
The trial and error process has been going on as long as we’ve been around and religion formalizes the teaching and adherence to those behaviors that have been discovered to work best. I know, it’s not perfect because people like complicate it. I think most religions have discovered good behaviors, and some do it better that others. Catholics do it best, of course.
One thing (I’m sure there are more) that secular morality has a problem with is recognizing the inherent worth and dignity of the human person. It’s hard to reason for someone being a “spark of the divine” if you don’t believe in the divine. I think Christians, specifically Catholics, focus on this the most. Without this concept we don’t have individual rights, or it’s very hard to argue for them.