My short answer is that Washington is too chickenshit to enact proper cordon sanitaire. What the CDC agency heads were telling the media did NOT line up at all with what we were doing to protect our own. The labs had rigid shifts with specific cohorts swapping out every other day so we wouldn't expose each other. HR literally paid us 10 hours every week to stay the hell away from work and each other so we could look after our kids and elderly.
As for vaccine efficacy:
2) vaccination helps, but may not be as good against newer variants as you have noted (hence my initial remark about high mutation rates in respiratory viruses):
https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2791601
An earlier Danish study noting reduction of CoVID transmission in vaccinated households:
https://www.nature.com/articles/s41467-022-31494-y#:~:text=We found a vaccine effectiveness,when they were fully vaccinated.
2a) the claim that "most cases of CoVID are in vaccinated people" is technically correct. However, this observation ignores epidemiology! As of early 2022, nearly 80% of the adults in the USA have had their two-shot primary series. Yes most new cases of CoVID may occur in the now-vaccinated population. "Isn't this proof that the vaccines don't work?" you may ask. No. The people who get sick, in spite of being fully vaccinated, represent a vastly smaller percentage than those who got sick while unvaccinated.
https://www.kff.org/policy-watch/why-do-vaccinated-people-represent-most-covid-19-deaths-right-now/