This is what I no longer understand about mandator

This is what I no longer understand about mandatory vaccinations. The current vaccinations were developed for a strain that is no longer the dominant strain. Hence, that's why folks that have been vaccinated are now catching the newer strains such as the delta variant strain. I get it that folks in a high risk group may be better off with the vaccine regardless of anything. But, for folks in low risk healthy risk groups, why should they get a vaccination for a strain that is no longer the dominant strain? To me, its like asking me to get last years flu shot for this years flu strain. Anyways, maybe someone can explain if there's any benefit to getting a COVID shot if they are in a low risk group.