Animation earns its place when it answers a question the user was about to ask: where did that come from, where did it go, what is loading, what did I just change.
Everything else is cost. Motion delays interaction, competes for attention and ages badly. Our default is none; we add it back one transition at a time, and only when the static version is genuinely harder to read.
Fast, short, and covered by reduced-motion. If it needs a spec longer than a sentence, it is probably decoration.