When everything will use systemd (because all the "core system" is starting to depend on it, wayland included) how do you evolve out of it?
Rewrite the entire lower level of your system AGAIN?
That does not help evolving rapidly, in my opinion.
No, and I'm sorry I was not able to explain that properly. :)
We should not (re)write a lower level where all the components are so coupled we will be unable to change one of them with a better alternative without changing the rest.