Playgrounds are one category of common resource, and we should have way, way more of these. I see a bunch of people suggesting that workout equipment or libraries count, but that's not really sufficient. At playgrounds, it's common to have a structure for kids under 8 and one above. We actually should have more for teens and above. We SHOULD have all-age group play structures.

This article examines how teenage girls in particular, for instance, often lack welcoming places to safely hang out outside the home: https://www.bloomberg.com/news/features/2021-05-28/we-need-more-public-space-for-teen-girls

We should have more skate parks. We should have urban bouldering walls. Swimming pools and fishing holes, and public gardens along with structures for adults to play tag on. That would be an improvement on most urban landscapes.