Underrated stuff/ideas in worldbuilding

Worldbuilding can't possibly be as detailed as real life,that is obvious. But we can explore our Worldbuilding projects approach to some real world things,let me start by saying what I think worldbuilders can take some ideas from:

1-Slums: Huge gatherings of cheap residential structures,riddled with disease and often theft. Sometimes,they are great gatherings of tents,cheap brick or container houses. Sometimes,they are gigantic,crowded housing units,neglected by whatever authority used to preside there. In my Worldbuilding project,after the revolutions of the 2040's,the government of a certain country,named kyosei slowly collapsed. The nation of Kyosei was a despotic one,implementing thought policing chips in the brains of its soldiers,and directing nearly every bit of wealth towards its capital,an esteemed city full of high rises and everything a billionaire dreams of. The neglected portion of the populace,which was most of it,lived in slums,mostly that of the old capital city which was abandoned by the government. The state troops wouldn't quell crime in these slums,instead only acting if they sense anger towards the regime of Kyosei. This allowed multiple slum warlords to rise,and maintain de facto control of most of the land. As soon as the Kyosei government collapsed,the rivalling slum warlords then went into conflict,salvaging whatever technology was left of the old regime. This culminated into the war of 2049,where two giant warlord clans went into war with eachother,and devastated the cities and farmlands of nearly a third of the island of Kyosei.

2-Differing religious requirements to hold differing offices: Lebanon would be an example of this.

3-Major city ruins: In the 21st century,major cities getting abandoned is almost unimaginable,but it used to happen. Think of looking upon the ruins of a city,which used to be a major center of trade and wealth in your Worldbuilding project.