Personally, I don't support mandatory vaccinations, but having a relatively large pool of unvaccinated people increases the "field" for the virus to propagate in and, therefore, produce new variants that could potentially break through to both vaccinated and unvaccinated. Non-replicating virus cannot mutate.
... see above, the vaccines are non-sterilising so the virus is still replicating, and mutating, among the vaccinated so your logic is based on a fallacy
.... it maybe advantageous in these circumstances to maintain a pool of unvaccinated in case a mutant that proves to be extraordinarily deadly arises in the vaccinated population that is less deadly for the naturally immune, as an insurance policy for humanity