It's still not quite there as a platform for exploratory data analysis - you don't have the instant reactivity of either a fully-fledged web code editor from Observable Notebooks or the hot-reloading file-watching Observable Framework. And the new Jupyter Kernel for Deno + VSCode is a pretty smooth experience too.
So while I agree that the ergonomics for exploratory analysis is uhhhh bad, I don't think the _publishing_ ergonomics is that bad. In fact, they're good. It's just a single file! I don't need to maintain some massive toolchain or pay some 3rd party service to just send someone a graph and some data munging - I just lob a HTML file at someone over Slack or host it somewhere. And the flexibility to style the analysis means that you can publish in environments where styling is important (blogs, or as a research paper).
Thanks for the heads up about SliderServer btw, was experimenting with something similar with Jupyter: https://hello-notebook-http-mode.fly.dev/