The idea that Observable makes life more difficult for people (in the service of building a profitable platform) doesn't ring true to me, though. To return to what I said in the first paragraph: Observable is conceptually simple (and most parts of it already have third party open source implementations). D3 is as intimidating as it's ever been, but I think the complaint "now I seem to have to learn Observable as well as D3" is not based on a good faith assessment of the complexity of learning Observable, and shouldn't be seriously entertained. It's in the "petulant" category of complaints about software.
Having said that, Observable is not a mature system and there are some traps for the unwary: https://observablehq.com/@tmcw/observable-anti-patterns-and-... This kind of thing would certainly make me think twice about depending on Observable as a platform for a major project. There's a certain confidence in the act of name "anti-patterns" and "code smells" which belies the slightly ad hoc, provisional status of the platform.
And not everything is taken care of elegantly in Observable: making an animation tends to involve more JS control-flow tricks than would be ideal: https://observablehq.com/@mbostock/animation-loops
The idea that Observable makes life more difficult for people (in the service of building a profitable platform) doesn't ring true to me, though. To return to what I said in the first paragraph: Observable is conceptually simple (and most parts of it already have third party open source implementations). D3 is as intimidating as it's ever been, but I think the complaint "now I seem to have to learn Observable as well as D3" is not based on a good faith assessment of the complexity of learning Observable, and shouldn't be seriously entertained. It's in the "petulant" category of complaints about software.