To be fair to the person you're responding to, airbag systems in modern vehicles are a lot safer than the single airbag per front passenger in older cars. The original airbag systems were just a single bag that deployed at a single rate based on an inertia sensor. Modern systems have several bags with multi-stage deployments that are inflated depending on seat belt and weight sensors.
But yea, as for the rest of the "safety mechanisms" the only modern change that I can think of that's not easy to retrofit but is a huge safety boost is blind spot detection. As someone that drives older (and smaller) cars, being able to see the blind spot detection light on other cars' mirrors is always a bit of a relief that their car will notify them if they try to change lanes.
But yea, as for the rest of the "safety mechanisms" the only modern change that I can think of that's not easy to retrofit but is a huge safety boost is blind spot detection. As someone that drives older (and smaller) cars, being able to see the blind spot detection light on other cars' mirrors is always a bit of a relief that their car will notify them if they try to change lanes.