It might be childish, but I think the “act like an adult” (or not) is a good way to frame the bad behavior that’s been so present lately.

It encapsulates so much of how I want to describe things.

Selfish behavior - this adult is just a child who didn’t learn to share.

Mean and vindictive behavior - didn’t learn to empathize as a kid

Lying? You’re still a child. Grow up and then join the adults.