Seriously, what do people want? That nothing must be using Linux specific kernel features ever, because that is unfair to other OS's?
When I use gimp, pidgin, geany etc on a Windows desktop, it's because they consistently work well with a thin Gtk+ shim over Win32. That's without installing a Linux compatibility layer like cygwin.
If in future one has to install some cygwin-systemd abomination just to run Gimp, then free software will have lost a fan.
The problem is that nobody really develops for non-systemd distros anymore. Sure, a loud minority is constantly attacking systemd, but they don't bother with developing crucial software needed to run non-systemd distros, nor do they help upstream projects to support them either.
The reason why upstream projects depend on systemd, is because systemd provides essential low level stuff that nothing else really provides on Linux.
There will probably be no problem with running Gimp etc. on Windows (or OSX) simply because those OS's have the necessary low level stuff to keep modern software running, so the projects can just use that instead of systemd.