Changing the animation speed is a little-known trick with Android, and can often make your device feel faster. But if you want to make animations faster than normal, you are left with two options - 0.5x the normal speed, or completely turned off.
What if you want something like 75% normal speed? Well, it turns out you can easily set a custom animation speed. Reddit user quantumsuicide wrote a fantastic guide, which I have made a bit easier for ADB newbies here.
To get started, you need ADB installed on your computer. The official way to install it is through the massive Android SDK, but it's a bit silly to download the whole SDK for one tool. If you're on Windows, I recommend using Minimal ADB and Fastboot to get ADB.
If you are on macOS or Linux, you can use Nexus Tools to install ADB and Fastboot in seconds. As a disclaimer, I did make Nexus Tools, but I promise it won't hurt your computer. Some Linux distributions have ADB as an installable package as well.
You also need to have the 'Developer Options' enabled in Settings. To do this, tap 'About phone' in your Settings application, and keep tapping on the Build number until you see the "You are a developer" message.
First, plug your device into your computer. Then, go to Developer Options in the settings and turn on 'USB Debugging.' If you're on Windows, open your Start menu, search "cmd" (without the quotes), and press Enter. If you're on macOS or Linux, do a search for 'Terminal.'
With your console/terminal open, type "adb devices" (without the quotes) and press Enter. You should see something like this:
That means your device was successfully detected. Now, just type these commands one at a time, pressing Enter between them:
settings put global window_animation_scale 0.75
settings put global transition_animation_scale 0.75
settings put global animator_duration_scale 0.75
To set a speed besides 0.75x, just replace 0.75 with any value less than or equal to 1. If you want to verify the commands worked, you can use these commands:
settings get global transition_animation_scale
settings get global animator_duration_scale
At this point, everything should be applied on your device. The custom value won't show up when you look at the custom animation scale in the Settings, and tapping it from the Settings will revert the changes. The good news is that the changes you make in this guide will stick after reboots, so you don't need to do this again (unless you want to change it).