RNA is has a short life span. It needs packaging (liposome, exosome hull or virus hull) to survive outside a cell. These hulls have a short life span outside of a body. The only way for RNA to survive longer is to use the protein factories of cells to crate copies of itself. That's what viruses do, but that requires a much longer RNA sequence than the vaccines contain. The vaccines create antibodies against the Wuhan variant that don't affect the current variants. It happens that vaccinated people always produce the same old antibodies instead of learning to create new antibodies against the current variants (antigenic imprinting, https://infogalactic.com/info/Original_antigenic_sin). These people can get infected with SARS-2 and sched the virus for a long time (they are most likely the only reason that the virus still exists).