Agree with your points and I think fundamentally the issue with unikernels at this point comes down to: nobody has really done it right yet.

By which I mean I see two variants:

1- exotic and interesting and constrained but probably not applicable for people in the form of e.g. MirageOS. not applicable because OCaml just isn't mainstream enough

2- Or other systems which allow much easier porting of existing systems by providing a libc and extended set of "porting" libraries which end up by recreating huge swathes of what the operating system is doing already anyways, in order to make the existing application just cross compile and "feel at home". But in reality probably always in an incomplete or odd way, and now you're using someone's hand crafted set of compatibility libraries instead of a battle tested operating system.

I just think we haven't seen the right system, yet, which would probably be some specific application development mostly from the ground up in the context of unikernel, not the other way around. Potentially a set of constrained and targeted Rust etc crates built from nostd up + some services. I kept looking for MirageOS for Rust and haven't seen, instead saw stuff more like 2.