The OS shouldn't be making many big changes that force me to reorient. When I'm moving between different UIs I often want to compare them; animations make it harder to compare state A to state B. I can detect very fine differences between two images by switching between them within a second, if there's a 1-second animation it not only means it's going to add a second, it adds a bunch of visual noise which might make it impossible to be able to distinguish what's an actual difference and what's just noise introduced by the animation.

Try using a tiling window manager. I generally dislike animation in my UI, but when a window, especially an unexpected one opens up and changes your layout it can take a second or more to reorient and it can really interrupt your flow. Animation would alleviate that.

That said, I still prefer sway over the animated alternatives for other reasons.