The shots were developed against Wuhan Classic, and to only attack the spike protein.
The virus doesn't have to change - add, delete, recombine - much to evade immunity.
It's the equivalent of setting up a web site that allows anyone, but Samuel, to login with just an ID, and no password. Samuel may not be able to get through, but Sam and Sammy can.
They need to fully sequence all existing variants, and develop mRNA immunotherapies that recognize and react to more than just the spike protein in the virus.
The current regimen was a desperate emergency Hail Mary pass with new immunotherapies developed with new technologies against a new virus.
They were hoping for a one-and-done vaccine, but it looks like this will be more like the annual flu shot that varies from flu season to flu season based upon modeling newly circulating strains of flu virus.
The key metrics to evaluate the reduced efficacy are deaths, ICU beds, and hospitalizations. At this point it has been demonstrated that "fully vaccinated" and "boosted" individuals can acquire and spread Covid-19/SARS2.
The hopium felt good while it lasted for those few weeks in June/July.