Windows Server excels as a Domain Controller with its comprehensive set of tools to manage users and computers. There isn't another software package out there that has the capabilities Windows Server does when it comes to Active Directory and Group Policy. In addition, Windows Server has a massive tool set, thus increasing both its functionality and flexibility.
Unfortunately, the flexibility and comprehensiveness of Windows Server causes it to be overly complicated to set up and manage, especially for a small organization. In addition, for things such as a file server, there are other options out there that are easier to use and more affordable - specifically in the NAS (network attached storage) space where both Synology and QNAP have very attractive options.
Perhaps the most frustrating aspects of Windows Server are the unnecessarily complicated and confusing licensing terms Microsoft has put forth. Sadly, this is not unusual when it comes to Microsoft, as the licensing even for their consumer-oriented products is burdensome.