Edit-to the point of some of the comments, I’ve reflected and agree that the original statement is an unfair comparison. My apologies to the children.

The biggest letdown of growing up is realizing how immature and much worse behaved than children so many adults are.

Edit2- thought this was clear but I’m not talking about the “I’m a child at heart!” adults. They are some of the best of humanity and I think being an independent thinker that is always exploring and leaning is a wonderful thing. I meant adults throwing tantrums to get their way, like the 50 year old screaming and throwing things in Costco because they were asked to wear a mask during a pandemic.