Yes, this was a big change and quite a shock for anyone expecting to be able to use the docs to learn d3 for use in traditional web apps, the way they used to u

Yes, this was a big change and quite a shock for anyone expecting to be able to use the docs to learn d3 for use in traditional web apps, the way they used to use the d3 docs. Personally I think what happened is that the DOM-manipulating and animation parts of d3 (but not the utility libraries) became existentially threatened by the rise of the component-based reactive JS frameworks, and the d3 authors made the reasonable decision to accept that, explicitly target a data science and academic audience, and create a for-profit company aligned with it. Maintaining docs targeting both use cases would have been expensive, and would have threatened the quality of the docs associated with their primary focus (observable), so they made the decision to accept that the docs would now be quite awkward for the traditional web app use case.