Why does Apple Music/iTunes sync playlists to my iPad but not my iPhone X?

Thanks for trying those steps and getting back to us Ty. It's appreciated. Since you're not using Apple Music, you can turn that feature off under Settings Music. 

Use iTunes to sync your iPhone, iPad, or iPod with your computer -- Since iTunes isn't syncing your playlists automatically, you can select which music you want synced. The steps to do so are under "Sync or remove content using iTunes". First, see if it will sync your entire library. If it doesn't, click the box to the left of "Selected playlists, artists, albums, and genres" and choose all the music you want to sync to your phone.

Get back to us with the results when you're able.

Cheers!

Greetings, Spencer.

I see that you're unable to sync playlists to your iPhone X. It works fine on your iPad, and I'm glad to help with this.

Turn on Sync Library with Apple Music -- If you subscribe to Apple Music, go to Settings > Music, and make sure that both "Show Apple Music" and "Sync Library" are both on.

Sync your iPhone, iPad, or iPod using your computer -- If you're syncing your iPhone with your computer, restart your iPhone first, then see if you're able to sync.

Let me know how that goes.

Take care.

You’re welcome, Ty. We’re glad we could help.

Have a great day!