I grew up with this animation so I didn't consider it annoying until I bought a new Macbook a couple years ago.
I noticed sometimes I would press keyboard shortcuts before my system's focus had switched. Just little stumbles here and there, some inoffensive, some annoying, but who knows maybe I didn't catch enough sleep.
Over time it happened often enough that I decided to google it, and it turns out my muscle memory wasn't failing me; the animation speed did change ever so slightly and was slower in new Macs with 120Hz displays [1][2] (newer MacBooks, 2021+). If you switch your screen to 60Hz it goes back to the faster animation.
Why is this animation slower now, and why does it depend on screen refresh rate? I have some technical theories but can't think of an organizational reason it happened and hasn't been fixed 5 years later at a 3.82 trillion market cap company. If you Google it there's plenty of discussions online about this. It's noticeable and annoying to people who have used the feature often enough.
[1]: https://discussions.apple.com/thread/256124324?sortBy=rank
[2]: https://www.youtube.com/watch?v=gNBWt4NvqHg