Content types enable you to organize, manage, and handle content in a consistent way across your sites. Content types can be managed in a central site called Content Type Hub. The Content Type Hub automatically publishes content types to all sites that subscribe to the content type updates. More details here.
What We Are Changing
The Content Type hub will no longer publish content types to OneDrive for Business sites (formerly known as MySites) by default. This change will increase the reliability and performance of synching content types to sites. It is rare to use content types inside OneDrive for Business, so for most deployments, these performance and reliability improvements should have little or no impact.
Other than increased performance and reliability, this change includes no change to content type publishing in sites outside of OneDrive for Business.
This change will start rolling out from 31st December 2018.
To continue syncing content types to MySites
In case you still want the Content Type Hub to push content types to OneDrive for Business sites, you can set a tenant property using a PowerShell command:
If you set this property before this change starts rolling out, then your environment will not be affected, and content type publishing will continue to work in all your sites as it does today. You can set this property at any time in the future and content type publishing will resume.
Once you have enabled Content Type publishing to OneDrive for Business sites, you can disable it later using Powershell command:
Sensible change and appreciate the fact that you've not shut the door to organizations who need bespoke Content Types in their OneDrive estate, Looking forward to the performance improvements elsewhere as a result of the change.