Slice units only help with resource allocation, but the main draw of Docker isn't that, but the fact that you can be running a completely different distro with

Slice units only help with resource allocation, but the main draw of Docker isn't that, but the fact that you can be running a completely different distro with a completely different stack since a container is basically a glorified chroot and that the image can be built from an easy to understand script and then shared with others. Sure, you could publish your app as a .tar.gz of the filesystem root and then users could extract it and have a script to bind mount everything and chroot into it. You could then set up a systemd service(s) for that script and set up a slice. But then you're just reinventing Docker from scratch for absolutely no reason. You could also use systemd-nspawn, but then you're losing out on a bunch of really useful features that the devs omitted because of philosophical reasons (as usual with systemd, they think they know better than you).