81 years is good. The average life expectancy is bound to flatten out some time I guess.
What do they expect? That the average life expectancy should keep rising into the 100's and beyond? And....what for? Dying is a reality. Merely extending old age further and further does not add any value either to the individual or to society.
The question raised in the article is whether the UK is performing badly here because of govt policies. I'm not entirely sure it's the case as I think it looks to be performing similarly to Germany. Indeed as mentioned but not looked at in detail in the article the US is going down at a surprising rate.
As to the aims of life expectancy, while it's possible to accept in the long run we are all dead, the extensions to life expectancy we have seen over the last 150 years or so are not about some grand plan to push the life expectancy figure up but about solving issues such as starvation and specific diseases.