There are different levels of mitigation. But yes, I do think we should be looking even higher than 70% of total population... Recent studies with the Delta variant suggest we need an 85% immunity level for herd immunity. While some of that will be naturally acquired immunity, we are probably looking at needing 70-75% of the total population fully vaccinated (not just first shot).
Sadly, we are unlikely to ever get there.
No, that doesn't mean we all wear masks and socially distance forever. It does mean that unvaccinated people should continue to wear masks (though they likely won't). It does mean that masking should be mandated in some crowded indoor situations (such as air, train and bus travel). It means surveillance and contact tracing should continue. And it means we really could benefit from vaccine passports, but we know that's not happening.
Essentially, sadly, the US does not have the willpower as a community to do what needs to be done -- Too much vaccine hesitancy, and the lack of the will to do things like vaccine passports to push the issue. Free beer and lotteries only entice so many people to get vaccinated.
Vermont has 66% of their entire population fully vaccinated. Not just adults -- Not just 1st shot. 76% of adults are fully vaccinated. So it's quite likely they will surpass 75% of the entire population as fully vaccinated once kids can get vaccinated. (If they get vaccinated at a rate even close to their parents).
So getting 75% of entire population vaccinated is an obtainable goal with the right cultural attitudes. Sadly, we are unlikely to get there on a national level. And we will pay the price -- Covid will likely stick around in various forms. Not nearly as deadly as in 2020 -- Lots of people with immunity, better treatments, etc.