Systemd is not a single binary either. It is many binaries, every one of them does its clearly specified job and together they live in single repository - just like coreutils.
The number of binaries isn't relevant. Claiming that systemd follows the unix philosophies[1] because it has "many binaries" suggests you don't understand that philosophy.
The point is limiting complexity. Smaller, self-contained programs are a lot easier to understand and debug than both a single "kitchen sink" app and a collection of tightly coupled programs and libraries.
If systemd followed the unix philosophy, I should be able to use journald in isolation. Or I should be able to use the init tools just as without bringing in the other tools. The point of a modular design is that each module should be as independent as possible so they can be replaced piecemeal and tested/debugged in isolation.
It doesn't matter if you split the project up into different binaries/etc. Busybox, for example, shoves everything into the same binary, but it's a modular design where it's easy to leave out any module and use the coreutils version instead.
[1] http://www.catb.org/esr/writings/taoup/html/ch01s06.html
I find these kinds of discussions a bit strange. I don't want it, it's made my system both less stable and less easily to hack around with. So I'm not going to use it. If you like it, go for it!
Good luck trying that with systemd...