I mean they do have universal basic income on earth but apart from that humanity is all kinds of fucked. And it doesn't exactly get better as the story progresses.
The earth is united like the United States is united. The tribes just got bigger is all. Instead of NATO vs BRICS, the Expanse universe has Earthers vs Martians vs Belters. And people are suffering hard on earth as evidenced during Bobby’s trip to the ocean.
Example B of earth being shittastic is the entirety of The Churn novella
The story for The Churn is entirely Earth based and provides a description of what the average life in a crowded, metropolitan city is like in the world of the Expanse. The city of Baltimore has given way to a multitude of crime bosses, and organized black markets. There are multiple bosses who each keep a "family" of personal guards that operate the smuggling of goods, illegal memory implants, weapons smuggling, cybernetic implants, and other illegal goods and services. The story takes place over the course of about two days.