You cut out some important parts of what you are quoting from. Although I can understand the confusion as the naming is less that stellar in this case. Let me quote part of this[1] in full and give a quick explanation of what's actually meant by it.
> systemd is a suite of basic building blocks for a Linux system. It provides a system and service manager that runs as PID 1 and starts the rest of the system.
What is being said there is that "systemd" is the name of a suite of tools (not all of which require or depend on each other, a number of them are entirely stand alone which have been adopted by the project) for Linux. Said suite provides a system and service manager that runs as PID 1, which also happens to be called "systemd". The "systemd-resolved" package is a completely separate service to the "systemd" init service, but both belong to the "systemd" project.
This is, for instance, similar to projects like KDE's Plasma which is the umbrella project for a number of related projects but also happens to be the name of the specific desktop shell.
Edit: If you really want systemd without resolved you simply pass in the --disable-resolved flag and it will build without it. It turns out that it's useful to have most of the default things systemd provides so Debian and Arch provide pretty standard builds which include resolved though.
Edit 2: If you really want to get dirty and you have the know how you can even look at the source[2]. Resolved is in its own directory and a (really) quick glance seems to indicate that it's largely independent apart from being in the systemd src/ directory.
[1] https://freedesktop.org/wiki/Software/systemd/
[2] https://github.com/systemd/systemd/tree/master/src/resolve
