I have had the experience with creating https://swiftbook.dev/learn

Used Codex for the whole project. At first I used claude for the architect of the backend since thats where I usually work and got experience in. The code runner and API endpoints were easy to create for the first prototype. But then it got to the UI and here's where sh1t got real. The first UI was in react though I had specifically told it to use Vue. The code editor and output window were a mess in terms of height, there was too much space between the editor and the output window and no matter how much time I spent prompting it and explaining to it, it just never got it right. Got tired and opened figma, used it to refine it to what I wanted. Shared the code it generated to github, cloned the code locally then told codex to copy the design and finally it got it right.

Then came the hosting where I wanted the code runner endpoint to be in a docker container for security purpose since someone could execute malicious code that took over the server if I just hosted it without some protection and here it kept selecting out of date docker images. Had to manually guide it again on what I needed. Finally deployed and got it working especially with a domain name. Shared it with a few friends and they suggested some UI fixes which took some time.

For the runner security hardening I used Deepseek and claude to generate a list of code that I could run to show potential issues and despite codex showing all was fine, was able to uncover a number of issues then here is where it got weird, it started arguing with me despite showing all the issues present. So I compiled all the issues in one document, shared the dockerfile and linux secomp config tile with claude and the also issues document. It gave me a list of fixes for the docker file to help with security hardening which I shared back with codex and that's when it fixed them.

Currently most of the issues were resolved but the whole process took me a whole week and I am still not yet done, was working most evenings. So I agree that you cannot create a usable product used by lots of users in 30 minutes not unless it's some static website. It's too much work of constant testing and iteration.