1. Delight is overblown, in my opinion. I think most of the people truly delighted by fancy animation are just other designers.
2. It's more useful to think about state when deciding when to animate. Could the user have trouble perceiving the change in state that just occurred? If so, then use an animation to help them visualize what happened. I believe this is the primary reason to use an animation - all others are vanity.
Isn't this just very basic optical feedback to indicate that a component is clickable at all and that the click was registered?
In a nutshell: put two different frames in sequence, and you have an animation.
Animation is when more than one consecutive step happens on it’s own. I’d argue that even tooltips appearing and disappearing after a timeout doesn’t constitute an animation, because the disappearance isn’t immediately consecutive with the appearance, and (maybe more importantly) the intervening state of the tooltip being shown is meaningful to the user as a distinct state.