Yep. Assuming no change with time, actuaries have come up with a lot of ways to predict deaths in an age cohort. But there is a problem in that medicine and economic growth have been improving human survival rates. To a large extent, in the past few hundred years, this has taken two forms, reducing infant mortality, and reducing overall mortality regardless of age. In the bathtub plot, this causes the left side and bottom to drop, but when you get above 70, age related mortality kicks in, and most members of a cohort die at about the same age. Decades ago almost everyone reached 60, very few reached eighty.
Now medical research is beginning to make a dent in elderly death, and there are a few problems when you try to describe 1) what the real mortality assumptions should be for young people today. They did not have a lot of diseases which were common when I was a child: measles, chicken pox, rubella, mumps, etc. How did these effect our health in old age? Shingles in old age requires that you had chicken pox. 2) what happens when you have a step function in mortality? (The death rate spikes or drops suddenly.) A lot of mortality models give nonsense results. We have had some (small) effects like that--the influenza pandemic of 1918 (one hundred years ago) dropped calculated life expectancy in the US by 12 years, but the reality was closer to 3 years before the pandemic, and an increase in life expectancy if you survived the epidemic. 3) When the decrease in death rates is huge the calculations break down entirely.
Let's say that next year someone develops a technique to cut deaths from heart disease by half, and someone else finds a cure for most cancers. Did you suddenly become immortal? No. But if a few people in your cohort live for a couple thousand years, there will be an unrealistically high life expectancy because the average (mean) age at death goes to infinity due to those few outliers, while the median may only increase by a few years. (And Alzheimer's becomes the number one cause of death.)
That's why, even though actuarial tables have been around for a century or so, there is still a problem of coming up with a useful number telling you about how much longer you will live. (Assuming you will live as long as your parents or grandparents is a reasonable place to start. Genetics does count. You may need to correct by dropping out those who didn't die of old age.)