<sigh> I mean that ChatGPT sounding like a "marketing ad copy robot" is not an inherent limitation of ChatGPT, it's merely the finishing stage of its training process. If OpenAI wanted to, they could have a hundred ChatGPT flavors.
It’s true that OpenAI can change it radically by tuning, but to a very significant extent users can change it by prompting (which is more actionable for people building apps on top of the chat models) but lack the ability to do tuning (which OpenAI makes available for the base GPT-3.5, etc., models but not the chat models, including GPT-4, which is currently available, even via the API, only as a chat model.)