OK, think it through...
How do we determine that a specific instance of a filesystem mount is "remote", or even requires a "network"? Consider that the network endpoint might be localhost, a netlink/unix/other socket, or, say, an IP address of the virtual host (practically guaranteed to be there and not truly "remote").
systemd has .mount units which are way more configurable than /etc/fstab lines, so they'd let you, as the administrator, describe the network dependency for that specific instance.
But what if all we have is the filesystem type (e.g. if someone used mount or /etc/fstab)?
Linux doesn't tell us that the filesystem type is a network filesystem. Linux doesn't tell us that the specific mount request for that filesystem type will depend on the "network". Linux doesn't tell us that the specific mount request for that filesystem type will require true network connectivity beyond the machine itself.
So, before/without investing in a long-winded and potentially controversial improvement to Linux, we're stuck with heuristics. And systemd's chosen heuristic is pretty reasonable - match against a list of filesystem types that probably require network connectivity.
If you think that's stupid, how would you solve it?