When it comes to the problem of targeting, one interesting and promising tech is photochemical internalisation [https://en.m.wikipedia.org/wiki/Photochemical_internalizatio...], where you put the mRNA inside photosensitive molecules (and not lipids) and then shine some light on the tissue/organ where you want the mRNA delivered. Where activated by the light, the molecules then enter the cells, dissolves and deliver the mRNA.
The Norwegian company PCI Biotech has a tech they call fimaNAc for doing this with naked mRNA.
https://www.pcibiotech.no/nucleicacids
This presentation has a lot of illustrations and explanations:
https://www.pcibiotech.no/s/PCI-Biotech-SMi-RNA-Therapeutics...