Didi significantly reduced subsidies after Uber left the market - in Shenzhen at least this means prices aren't any better than taxis. It's usually faster to get a taxi in most places and times of the day than waiting the 3-5 minutes for your Didi to arrive. Back when it was a lot cheaper to Didi, people would wait a couple minutes to save 50%, but if the price is the same, they take what's faster.

On top of this there's additional competition from the huge numbers of people using bike sharing like Mobike or Ofo - which not only taking a bike much cheaper, but it's often faster because you avoid traffic jams.

Amazing how much the market has changed in such a short time.