I think the simple chat interface is why chatGPT became popular. If other people build relatively simple interfaces to leverage other models they might be successful as well.
I think it's the chat interface combined with memory. The second not many people had seen used in practise. The chat bot also generates much longer prompts, most other chat models seem to be trained for short prompts, and purely conversational.
As a user of both, I tend to prefer the playground for most productive uses. I think chatgpt is a very specific use-case of language models that's mostly just for fun, and Google searches- but even for that the playground gives you greater control.
Would you consider checking out my site aidev.codes? You can use text-davinci-003 or code-davinci-002 and it will immediately create and host pages on the site. Or you can just collect whatever files and there is a download button. I plan to add GitHub and a lot of other stuff.
I am not sure what is the framework you are using for your site but it is not very mobile friendly. There are many frameworks available that can make a responsive site without much effort and also set up SSO authentication for you (like one can use google to login). I will try it later from a laptop.Good luck!