"and exports clean code to be extended"
This is quite the bold promise and I'd use something like this if possible. But I'd rather just have a prototyping tool that I pay for once.
For a maintainable site, I'm not sure if APIs are needed. Maybe for a blog or ecommerce site that you're making an app for? Squarespace and WordPress already do this though, at a decent price, and it's easy to just hire a WP technician as needed or ask ChatGPT to debug.
Maybe figure out your target market, as there might be conflicting models here.