Why do you say that?

Bubblewrap is a it's a very minimal setuid binary. It's 4000 lines of C but essentially all it does is parse your flags ask the kernel to do the sandboxing (drop capabilities, change namespaces) for it. You do have to do cgroups yourself, though. It's very small and auditable compared to docker and I'd say it's safer.

If you want something with a bit more features but not as complex as docker, I think the usual choices are podman or firejail.