Cargo containers are a standardized sizes and they fit a certain number of cars, the only way to fit more is to make cars small enough that they're simply unsafe in an accident.
Smaller cars are great. "Unsafe in an accident" is dependant on speed, and if you're just driving in a city you don't need a vehicle designed for highway speeds.
If you only drive in a city then you don't need to own a car at all, so that point is moot.
Small cars from the 80s/90s are a death trap even at slow speeds and making them safe requires them to be bigger, even if it's only for slow speed accidents. Heck, speed limits in cities can go as high as 55mph/90kph, that's pretty freaking fast and not a speed I would love getting hit at in a Kei car (my brother has one, you're safe in it because of how small it is and how thin everything is around you).
Small cars from the 80s/90s are a death trap even at slow speeds and making them safe requires them to be bigger
it's probably not the 90s you're thinking about.
90s cars had airbags, large crumple zones and seat belts. Those were pretty safe already. Maybe you are thinking 60s and 70s?
Yes, 90s cars were fucked if hit by 3t of steel at 180km/h, yes. But so are current cars.
And less heavy cars that run into you, made less safety needed. So if we were to build only light (say sub 1t and driving 80km/h max) cars to modern standards, we would all be way better off. But people are assholes, so that won't happen.
a high concentration of large lithium batteries might make the fire a bit worse.
so if this was 100% petrol cars, i think the risk and severity of fire is lower.