Again, yes. But it's not like there's a big conspiracy to push systemd in your systems. People (developers, distro mainteners, system maintainers, ...) are using it because for them it has value. It makes it easier, more reliable, whatever.
Many OSS projects require gcc, or glib. And can work with alternative compilers or libraries, but maybe you'll encounter some issues. By the same logic, would you say that GCC and Glib are reducing your freedom?
And by the way I'm not saying that the premise is false. It's true that it somewhat reduces your options. But you still have options.
And I think that having a somewhat standardized environment is a good thing. But if you don't, use another distro. Heck, use OpenBSD!
(I'm using "you" but I'm not referring to you in particular, it's an impersonal you)