Good question, @philnauta. My personal philosophy is that eye candy purely for the sake of eye candy is generally not a good idea. That said, animating certain UI elements in specific contexts can actually provide useful feedback, depending on the experience level of the user. A menu instantly appearing, for example, can be disorienting for some; so maybe sliding the menu in from offscreen enhances the UX.
However, something to be aware of with animations (as @anon65040322 has pointed out in this post) is that visual/layout glitches can result. My experimentation suggests that this happens when a second event is triggered before the first animation has completed - such as clicking a sliding menu icon in rapid succession.
If animation durations are kept reasonably short, however, it might never be an issue in the real world, but it’s something to be aware of.