speed makes software fast
Animation makes software seem slow. I think that half the time it is due to the animations actually causing lag, and the other half of the time it is due to the animations taking longer than the action needs to take.
I was using the Gnome desktop environment recently, and the animations would make my computer hang whenever I went to the birds eye view of all windows (I don't know the Gnome terminology). It would only hang for a very short amount of time, maybe a few milliseconds, but I noticed it. It looked slow.
Then I turned off animations. There was still a little hang, but the process felt so much faster. This is anecdotal. I'm sure I'm not alone. To prove this thought just for myself, I tried it on other software - KDE, Android. Removing transitions feels faster. No contest.
Another place where I bet that this is the case, but that I couldn't test in the same (rigorous, highly scientific) way was in web applications. Pinboard feels fast. It's ugly and dense, but I use Emacs, that's my jam. When I delete a bookmark, it disappears, bam. When I add a tag, it pops into existence. Bam.
Material design suggests that everything should come from a physical place and go to a physical place. That's all very cute, but it feels slow. The GMail web application has interface bits swooshing in and out from all over the place, but it doesn't feel coherent, it feels like a piece of art. It's not a tool, it's something to look good and mystify onlookers.
When an animation is happening, I (aka the user, the person the software is built for) am out of control. I can't do anything. I hit the keyboard, but my processor is to busy dancing with my browser window to pay any attention, as my terminals neatly arrange themselves in a flower shape. That's adorable. It's like the little whistle button on the Mii channel. The thing is, I press the little whistle button for entertainment, to see the caricatures of my family nervously run into lines based on what colour their shirts are. When my window manager does it, it feels like a caricature of the productive working session I was trying to have.
Oh and also, that swooshie touchpad move on Macs? Doing that on a twenty inch monitor makes me seasick, and I don't even get seasick.