Three animations carry meaning. Everything else costs time.
Which animations carry meaning, and which don't?
The first is the build, in which parts of a slide appear in the order the speaker reaches them. Its value is that the slide never contains information the audience hasn't been told about. That's an effect on comprehension, and the arithmetic makes it concrete. Use a build when a slide's content really is sequential and the speaker is in the room. In a document that's read on its own, it's worth nothing.
The second is emphasis on the object the sentence is about, used once on a slide, usually as a colour change or a subtle size change. It points the audience's eye and the speaker's sentence at the same thing at the same time. Used twice, it's a habit. Used on every bullet, it's noise.
The third is motion that shows a real movement, meaning that something in the content actually moves: a position on a matrix that changes between two years, a value that travels from one column to another, a component that detaches from an assembly. If nothing in the content moves, motion is a lie about the content. A still slide tells the truth faster.
Against those three sit the effects that exist because a menu needed filling. Bounce, spin, swivel, grow-and-turn, boomerang, blinds, checkerboard, random bars, wheel, dissolve-in, fly-in from off the slide, and the letter-by-letter typewriter reveal. That's twelve effects with no meaning between them. Each one costs the audience the seconds it runs, plus the attention it takes to work out whether the movement meant anything. The test is blunt, and it works. State what the audience learns from the movement. If the answer is a fact about the content, keep it. If the answer is that the slide is now more interesting, delete it.
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How should you time the animations you keep?
Two more habits keep the surviving animations safe. Keep timing short enough to be invisible, somewhere around 0.3 to 0.5 seconds for an entrance, because an animation you notice has taken over. And give every animation a still version that isn't broken. The deck will be exported to PDF, printed, forwarded and read on a phone, and in all four of those the animation doesn't exist. On the audited deck, 61 effects went to 9, a deletion of 85.25%, and after the pass only 3 of 42 slides carried any animation at all.