Hello smichaellutz,
Thank you for using Apple Support Communities! I understand that playlists created on your iPhone no longer sync to iTunes. You've come to the right place for help.
Do you have or did you previously have an Apple Music or iTunes Match subscription? The reason why I ask is that with music specifically, iTunes is designed to sync one way. This means that you can sync music from iTunes to your iPhone, however it does not support syncing music from the iPhone to iTunes:
Sync your iPhone, iPad, or iPod using iTunes on your computer - Apple Support
If you have an Apple Music or iTunes Match subscription, you can however use iCloud Music Library to keep your music up to date across all of your devices. Turning on iCloud Music Library on both the iPhone and in iTunes would ensure that playlists you create on the iPhone are synced to iTunes and vice versa:
Sync your iPhone, iPad, or iPod using iTunes on your computer - Apple Support
Cheers!