While that's true, we didn't have as many major centers with permanent buildings set up. I'm looking for data, but I imagine that places like New York would be underwater, would they not?
Sea level rise is measured at 3.5mm/yr[1] as of 2016 so at current rate it will take 2000 years to hit 7m. NYC may be underwater but it would in all likelihood be as irrelevant to the future as Tyre or Carthage is today.
The concern is the acceleration of the sea level rise
"Whether it takes another 200 or 2000 years largely depends on how quickly the ice sheets melt. Even if global warming were to stop today, sea level would continue to rise."
Given the semi-permanent nature of changes at this point we should likely start talking in rates of change.
7 meter rise over 2 centuries can likely be managed in a reasonable manner via land taxation, resettlement, wall, and levy construction. 7 meter rise in 5 years would likely collapse most of the western world as major population centers find themselves unlivably under water.