Power grab as in taking away user's freedom to: choose their own init system, or to freely and transparently edit and organize the startup of their systems.
One of the ostensible reasons for systemd was so the system would boot more quickly. But my systems boot up more quickly when I use System V init rather than when I try to use systemd.
@Pat it's an amazing daemon management and init system, organising that mess is a pretty damn good reason for existing. What do you mean by power grab though?