Not going to disagree with your post (you're spot on) but in response to that one sentence: systemd.
I'd actually be rather surprised if it wasn't possible to boot an entire modern Linux-based OS with zero GNU components these days. The shell environment would likely be rather unpleasant, but then the cutting-edge GNU/Linux shell environment is already unpleasant to 99.999% of human beings, so no big loss there. I bet you can boot up Linux, get into X11, and have a working KDE desktop without any "official" GNU components, right now.
Obviously, _building_ a modern Linux-based OS without using GNU software is still utterly impossible.
