The code isn't good enough nor does the AI have a good enough understanding to implement the code itself. It's all quite basic code and often has errors.

The OpenAI team might be using ChatGPT to help design the next iterations but it's not exactly possible to "cut out the middleman" at the moment All the games/programs that have been made using ChatGPT have only been possible because people can actually check if the code is good, see if the program works and write followup prompts if necessary. It's not within ChatGPT's capabilities to actually see if it's code works. It may spit out a working answer sometimes but it can't actually test if it works itself and as such it can't improve without the aid of a human.