Good use of manager time is to figure out what those people do differently and then have them teach their ways to the others. This will, in effect, "improve the whole system" as someone else put it.
Put another way: when there are individual 10x performers on the team (note that this is 10x the average, not 10x the worst), there is also massive untapped training potential, and management has already failed to make use of this. If anyone should have a bad performance review in that situation, it sure isn't the individual contributor who didn't get the tools they needed to do the job! It should be the manager who didn't give them those tools.
That said our business has a tendency to overvalue individual contributions over team contributions. My going example is that a person that spends all day getting other people unblocked on their issues might well be the greatest facilitator of productiveness in the team, but they will appear to be the person that never gets anything done.
What if the greats do that, and the others just don't care enough to learn, like this is a blue collar job with white collar pay to them?
They could be greater than they are; they think they're great already, but they're nowhere near the true greats on the team.
You can't make them care and you can't make them want to be great.
In a great workplace, people start to care. They feel pride over their workmanship and social responsibility with other employees. (In general. As always, there are outliers that need to be handled differently, but they're a small minority.)