You Can Downgrade
If you can't stand Android Oreo's performance (or features) you can try dropping down to Android Nougat (or and older version of Android Oreo) to see if that improves things.
If you’re unfamiliar with how the Android downgrade process for Nexus devices, take a look at this guide, courtesy of the Nexus Help Forums.
The walkthrough will take you through the steps you need to take in order to move off the current version of Android you're currently running.
There's no guarantee downgrading to Nougat will help, but it's worth a shot if you simply can't stand Android Oreo on your Nexus 5X.