Splitting something into multiple executables doesn't make something not monolithic just like splitting a program into multiple source files doesn't make it not a monolith. It's not a monolith when the different component parts can be cleanly factored out, replaced, and used outside of the original context or with different versions of related components This is in fact very hard. Much harder than making a monolith.

For instance the X11 ecosystem isn't a good example of a monolith because its designed to make it trivial to swap in different loosely coupled components. You don't worry about needing your window manager and X11 to come from the same commit so they actually work. You can argue that the toolbox that systemd provides it is worth it but arguing that it's not a monolith just screams I'm not a developer.