I'm glad to hear that others are equally frustrated with the tight coupling between D3 and Observable.

For me, it just wasn't worth the effort of learning D3 AND Observable (especially, not being particularly fond of JS to start with) - in the end, it was too much, and I ended up using a simpler third party javascript charting library instead - which was a real shame, because I really loved what D3 could achieve.

Mike Bostock is clearly a genius, but I think his brain is wired differently from the rest of us mere mortals - and unfortunately, he seems to have the knack of making simple things terribly complicated.