You won't stop mutations. It's a pandemic, world-wide - and short of blocking all international travel, freight/shipping, etc - if there is a new mutation somewhere in the world, it will eventually land here in the US.
Herd immunity - either reached by vaccinations, previous-infections, or both - is all we can hope for.
Good news is, we don't need unvaccinated people's cooperation to reach herd immunity - they will eventually have natural immunity anyway.
Of course, we can never stop all mutations. However, for mutations to be useful for the virus, they do need to happen at an evolutionary scale. Especially because we're lucky that SARS-CoV-2 mutates much slower than Influenza and HIV.
If the rate of transmission reaches the elusive herd immunity, the time-frame for the virus to evolve into evading vaccines grows significantly longer, even with a non-zero mutation rate.
Lastly, antibodies created via the mRNA vaccines have a broader binding affinity to different variants than those from natural immunity [1].
Again, the goal is to not eradicate, but to scale it down to the point where it is statistically not a threat.
Your original point was we got lucky with the Delta variant because our current vaccines still work.
I'm saying it doesn't matter - even if we had a 100% vaccination rate, some new variant will develop someplace that's being ravaged right now (say, India) and spread to the US eventually anyway. If our vaccines still work - great... if they don't, well.. where are we then?
Lastly, the numbers already indicate it's statistically not a threat to the overwhelming majority of the US population as-is.
I wasn't talking just about the US, I think we need very high levels of vaccination everywhere to make it statistically not a threat. We need to control the spread of the virus to levels where it's not mutating at evolutionarily scales, _everywhere_, and the only way to effectively do that is vaccines.
It's not a threat at this very moment, for this very point in time, but since we're allowing the virus to spread at such evolutionarily scales, inside and outside the US, a new variant popping up that evades vaccines is statistically very possible, and pose a significant threat to my own and society's well being.
I'm trying to argue that this is not a personal choice issue, rather a public health one.
Herd immunity - either reached by vaccinations, previous-infections, or both - is all we can hope for.
Good news is, we don't need unvaccinated people's cooperation to reach herd immunity - they will eventually have natural immunity anyway.