Not that many people keep large distributed workloads anymore, and SLURM-like schedulers on top of regular operating systems were deemed good enough for supercomputers.
The Cray T3D had a really nice distributed services model (really kind of a distributed exokernel) that would be worth emulating
on some machines there was an interactive ganged run facility like 'mpirun'. I think even this distinction where there are 'login' or 'service' nodes and anonymous runners would be at least a little structure. I guess you could argue that k8s is this, but it kind of falls short and seems to require a lot of continuous propping up.
I worked on a single system image project that didn't ever get shipped. it turns out that a syscall proxy layer isn't that difficult to implement, and that leaves you with an undisturbed user space.
anyways, there are a whole host of design options that don't look like k8s or slurm. and having spent some time recently on non-hyperscaler clusters, that bottom level of bringup (provisioning, networking management, reporting, fault tolerance, distributed filesystems) is really a nightmare. I think we lost a lot of traction there by raising generations exclusively in someone else's operational context.