And people are also telling you that tight integration is not a mandate. Having a bunch of stuff designed to work together does not mean that they're tightly coupled and can only work with their specific implementations.
We've all got confirmation bias, the trick is to be aware of it.
You aren't making any sense. All of the components of system D are separate programs, and yes they are maintained by the same general project and designed to integrate well with each other, but just because components are designed to integrate well with other components from the same project if they are present, that doesn't remotely mean that all of the components are required. And I mean, the proof is in the pudding, there are plenty of distros that do not use all of the components of systemd. Also, doesn't Linux have a long history of creating integrated suites of programs designed to integrate well with each other and used together? Like GNU?
We've all got confirmation bias, the trick is to be aware of it.