Disclaimer: I've only been in China for a week so far, so what I can tell is just what I see (besides what everyone hears in Western media, that is) and it may be biased.
Shenzhen is a city of many contrasts. I work in a relatively modern office building and live in a not-totally-crap hotel. I travel to work via taxis which seem to be staffed by poor people trying to make a living. Forget about Uber here.
When I get out of the hotel, I can turn left and find myself next to KFC, Starbucks and a big shopping mall full of expensive-looking clothes. Everything is plastered with ads like you wouldn't believe. Or I can turn right and find myself on a poor street that is flooded with trash and occupied by tons of people selling absolutely everything - meat, fruits, phones, barber services. Those people look impoverished and from what I can tell, pretty much sit there 24h/day 7 days a week trying to sell something to someone. They are all incredibly friendly, but you can feel the lack of perspective for a better life; it's heartbreaking. There's a family of street food vendors making fried pasta with various meats; a father, a mother and a son. I'm buying food from them pretty much every day. They're extremely proficient at what they do (and they use up scary amounts of propane for that), but you can see that they'll be doing it for the rest of their lives.
There's a big construction zone next to a metro station nearby. They'll probably be building skyscrapers, like a lot of others that are currently in progress. The zone is fenced off with 2m high concrete walls. I managed to take a look through a crack, and what I saw was something akin to a labour camp. Some metal sheds, minimum sanitation, lots of people cramped together. I've been told they're workers from local villages. They looked hungry and impoverished. They don't seem to have any safety equipment.
There's a fucking Starbucks and a KFC and lots of people with smartphones few hundred meters downstreet. And a modern, high-tech metro station on the other side of the wall.
Then there are electronics markets. Tons of fancy stuff. Everything you could imagine. Sold by people cramped together in small spaces that look like they couldn't afford what they're selling. Basically third world selling first-world products.
It's really unnerving that you can have a place that is so amazing and yet so sad at the same time, with nothing but an occasional concrete wall separating the two pictures.