Observable is fantastic, but as others have hinted at, IMO, I think it's trying to lock you in. I want the raw JS, in one click, so that I can build out a visualization locally, just hacking on HTML/JS. Steps to doing this are highly obfuscated when they could be a single button.
Overall you can see its evolution from prior sites- someone spent a huge amount of time demonstrating cool visualizations, then tried to make it all "proprietary". Nothing wrong with that, but why not make people addicted to the service by giving them the raw drug, rather than making them hate you for dancing through hoops?
Again- huge fan of access to many cool visualizations that have greatly improved what I can express visually for presentations etc., but very unhappy that I can't do this so much easier for my particular workflow. I'd love to be shown otherwise, but I've also spent a lot of time looking for answers, reading forum responses, etc., and they seem to all reflect wanting you to go through them, not along for the ride with them.
I'm building something similar called Starboard Notebook[0] that has a different set of trade-offs. It ends up being something in between Jupyter and Observable:
* One of the goals is to build Jupyter how it would have been if it was designed for the web (only).
* It's open source [1], plays nice with git (the format is plaintext), and supports local viewing & editing [2]
* Because of that you can host it yourself, put it on your blog / github pages, anywhere.
* There is little magic, it actually is just Javascript at it's base. This means you can use standard browser APIs and HTML, and when you are ready to "graduate" the notebook implementation that should be straightforward. In my eyes notebooks are only for the first 20% of the work that does 80% of the job for small applications/experimentation (which is often where it ends anyway).
* You can "build the ship as you sail": you can load new cell types dynamically at runtime. This is also how Python is supported (through WebAssembly).
* You can have interop with Python and Javascript which is really powerful. Example: Create a drag an drop form using HTML+JS, then process the dropped CSV file using Pandas and visualize using matplotlib.
[0]: https://starboard.gg [1]: https://github.com/gzuidhof/starboard-notebook [2]: https://github.com/gzuidhof/starboard-cli