Masks are PPE, and PPE is typically a poorly effective means of hazard control. Cloth masks were always known to be poorly constructed for their intended purpose at that even... But really was a "better than nothing" solution that's easily accessible and implementable (unlike building ventilation systems.)
Vaccines are highly effective, and continue to be as long as we have realistic expectations of what they do. Preventing all infections is not realistic.
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Vaccines aren't effective against Omicron because it evolved. Organisms do that. It's been happening since before the first primordial sludge crawled out of the ocean. And it's happen in large part due to the anti-vaxxers refusing the vaccine, thereby causing strains to mutate.
There isn't evidence for this claim. The unvaccinated by choicers are a risk, but that's not where the variants of concern have come from.
Delta originated in India prevax rollout.
It's not been established where Omi came from, but leading theories are from an animal reservoir that crossed back to humans, or possibly from an immunocompromised human with a long running (but not lethal) infection that couldn't be cleared from the body.
Vaccines don't eliminate those scenarios. More vaccinations doesn't necc prevent new variants.
Higher vaccination rates create selection pressure for antibody evasion.
Delta is highly transmissible, but only mild reductions in antigenicity. Areas of high vaccination had only mild Delta outbreaks.
Omicron however evades effectively, thus the total cases shoot much higher and it outcompetes.
The problem with the unvaccinated is the risk to the medical system being overwhelmed during an outbreak due to so many severe cases. Not to mention the impact their illness and death does to their families.