Cars don't weigh substantially more than they did 20 years ago. Specific models do tend to gain weight over time, but that's not relevant if comparing the cars themselves. A 2000 Honda Civic is an entirely different car than a 2020 Honda Civic. The 20 year old Civic is more similar to the Fit. The 2020 Fit weighs as much as the 2000 Civic, despite being larger, roomier, quieter, and safer. It's not that cars have gained weight in the last 20 years, simply that massive vehicles boasting extravagantly obvious externalized safety problems are grossly irresponsible and popular.
What hasn't changed is a regulatory neglect of vehicle safety to non-participants. When a lifted Dodge Ram decapitates everyone in a Honda Fit, the statistical penalty is scored against the Fit. We don't measure safety like this in other regulatory domains. NHTSA used to provide crash injury and fatality data separated by occupants and non-occupants. I haven't seen that detail provided since 2008, but I'd be happy to be corrected if I'm wrong: https://cdan.dot.gov/query
That said, city streets that only had dense electric vehicles that don't go past 20 mph (maybe a mix of things like this and buses/streetcars) would be delightful.