Taking a modern Corolla and offset crashing it into an older Corolla and measuring the damage to occupants is entirely valid as an experiment, and saying that the equivalent occupant would be more damaged.
Safety systems that protect against trees and side of road stuff add weight, but they also mean that if you head smack the equivalent car from decades ago, then m1v1+m2v2=(m1+m2)v3, plus conservation of energy come into play, and the modern Corolla destroys an older model...Similarly, my 5 star Colorado and a 2017 5 star Corolla are going to feed physics into the equation as well, versus 5 star Corolla into concrete block.
Astro's point is also very valid...when I was in the "most likely to kill myself in a car" demographic, my cars were old, the suspension and bushes needed work (which I did), and were fatigued, and carrying rust...those cars were more dangerous than the day that they were made, and so was I.