Allow the use of Organizational Units for users and devices, whether synced or using Azure ADDS in Dynamic membership rules
OU's are the cornerstone of a well designed and implemented Active Directory Domain. OU's help ensure that when selecting users for a dynamic group, that we are not relying on information that may be inaccurate in a user's profile, such as Exchange Attributes, Departments or others. Any data that can be "typed" in, can be "fat fingered", and as OU's are normally static and not modified very often, they are a more trustworthy selection for determining group membership.
OU's should be a fully configurable and useable in Azure, in all situations, whether you rely on Azure AD Connect, or Azure ADDS. It is extremely frustrating that a resource that has worked well on thousands and thousands of on-prem Active Directory Domains is not availble in Azure.