I've had the goal to learn modern JS and D3 for a few years now. And I struggled with finding a good ressource as well.

Over the past year I've done it finally, and I can recommend the book "D3 for the impatient". It's written for D3 v4.x, but I wanted to write my project with D3 v6, obviously. Luckily, just going for it and googling the error message when I got the inevitable "foo is not a function" was easy enough. Now I'm confident enough with it that just reading the github readme of a new D3 module is usually enough to get me going.

But the API has quite a bit rough edges (like the difference between select and selectAll, the selection.merge(enter) pattern), that a good book is really nice. Especially since online tutorials are a complete mess - because of Observable non-sense and severe API rotting.