Turn down the animations of macOS

Go to System Settings → Accessibility → Motion and turn on Reduce motion. Windows fade instead of flying out of the Dock, desktops cross-fade instead of sliding past, Mission Control appears rather than unfolding.

Nothing is removed and no feature stops working; the transitions just get shorter and flatter. There are two good reasons to want that. One is medical: if you are prone to motion sickness or vertigo, a screen full of movement is genuinely unpleasant, and this is the setting Apple points you at. The other is that a system which stops animating feels faster, because you are no longer waiting out half a second of choreography every time you change space.

What it will not do, whatever you read, is meaningfully extend the battery. The GPU draws those animations and it is very good at it; any saving disappears into the noise. Turn it on because you prefer it that way.

Same panel, also worth a look: Auto-play animated images, which you can turn off to stop GIFs looping at you in Messages and Safari.

On macOS Sequoia and earlier, Reduce motion is in System Settings → Accessibility → Display.