Yes, renewable is cheap, but also unreliable. And storage to manage that unreliability is, per your link, more expensive than the corresponding fossil fuel plants. It's either that or drastically over-provision the renewables, which then has to be factored into the cost.

Right now, the cheapest approach from scratch could maybe consist of:

1. Over-provisioned renewables,

2. connected to a large-area grid to mitigate local-scale negative impacts to renewable productivity,

3. with enough fossil fuel capacity to basically serve as "storage" and bridge large-scale negative impacts to renewable productivity.

But, of course, China is not building from scratch -- they've been at this for decades. And the inversion of prices between renewables and fossil fuels is a fairly recent one.