You are absolutely right that cars are heavier now, which means they are putting more energy into a collision, but cars are also better at dissipating that energy. I don’t actually know enough to know what wins in that face-off. You could very well be right. I’d defer to someone with more expertise in collisions.
To be fair, I think people looked at the folks who were into mermaids as outlandish too. “Been around for a long time” doesn’t mean the same thing as “totally accepted socially”.