Minijail

* Static binaries (of course)
* Reliance on LD_PRELOAD which is essentially a user-tunable knob. Use of LD_PRELOAD should always be considered a hack, and since it is a hack, few hacky vendor scripts are written to set LD_PRELOAD (as they occasionally do) using something like "LD_PRELOAD=$LD_PRELOAD:...". And about that, stacking LD_PRELOADs is an analytical nightmare, good luck debugging a SEGV.
* Building essentially a system call interface emulator. The wrapper must ensure it catches every interesting syscall and regularly be audited to ensure the situation hasn't changed. Ensuring seccomp is enabled early is a nice feature here, but it doesn't avoid the architectural travesty of trying to mirror an interface that is a moving target
* Endless bizarre interactions due to messing with every program's runtime image. LD_PRELOAD causes process-visible changes during e.g. calls to dlopen()

I can't say I'd rely on any tool for general purpose use that is effectively exploiting a debug interface to work at all