UPDATE – Microsoft does not recommend deleting the root site and is working on native capability to create communication site at Tenant root for Q4 CY2019. Office 365 Roadmap
SharePoint Admin Center allows for creating the new Modern Communication site but only with a managed path prefix (/sites/ or /teams). However, there is a workaround by using the SharePoint Classic Admin Center to modify HTML <SELECT> control and add a new choice for “SITEPAGEPUBLISHING#0” web template. See video for full demo. Cheers!
Create Modern Communication for Root Site in Tenant from Jeff Jones on Vimeo.