It sure sounds like macOS Server isn’t long for this world. Apple has announced a number of services that are being removed from Server, including Calendar, Contacts, DHCP, DNS, Mail, Messages, NetInstall, VPN, Websites, and Wiki. In addition, FTP support and iOS File Sharing support were removed from Server back in September.
In the age of NAS devices like Synology that offer easy setup of many of these services, I understand why Apple is doing this. Still, there are bound to be many Server fans upset over the loss of features from a product that had a devoted following.
Apple has moved some Server features into High Sierra, making them available to all users. These include the Caching Service, which let users save bandwidth by having a Mac cache iCloud data, app updates, and more, for use by other devices on the network. File Sharing has also been moved to High Sierra, and Time Machine backups can be made using SMB backups built into High Sierra.
If you want to take a look at all the features that previously were in Server, the OS X Server features page is still online.