While life expectancy at birth has increased a lot, that was mainly due to infant survival rates. Life expectancy once a person reaches, say, 25, has not increased by that much.
Diabetes type II was vanishingly rare not long ago. Now we have teenagers suffering from it. Teenagers with Diabetes type II is not due to humans living significantly longer.
Similarly with dental caries, which is quite common in childhood these days. This is not due to people living significantly longer.
Similarly with Cancer. There are cancers that are relatively common in young people today. Testicular, or breast cancers occur quite often in young people. Missionary doctors in Africa, among the native Americans, or the Inuit, report not diagnosing a single case of cancer for years. It is not a matter of diagnostic failure. An untreated late stage breast cancer or testicular cancer is quite easy to diagnose.