I think it is smart, considering their resources.
They are putting their resources into the 2 aspects that make an invasion of their country either completely unfeasible, or a very costly prospect.
Their navy and air force thus take a distant back priority to land forces in the terrain they have, and a nuclear capability with the ability to deliver it on any potential invader, even if you ignore the bargaining chip that this obviously brings politically.
Whatever about other aspects of North Korea, I for one cannot fault the planning behind where they allocate their limited resources from a military aspect.
They seem to understand that big ticket naval or air force projects are pointless, considering their situation.
They seem to invest in sub warfare more than surface vessels (which would simply be targets), and may eventually "warm over" the air force, but clearly know where their priorities should be.
In my opinion, they don't need new Chinese kit for the air force, beyond an air policing role. Being next door neighbours to China is a thing all on its own.