Thanks for that. What do you think are the key heuristics / concepts that made it standout or be more appropriate for architecture diagrams?

before discovering d2, I wrote / vibe coded my own diagram generator: https://azriel.im/disposition

then after discovering it, I was too invested in my own project to switch -- the complexity in positioning nodes, routing edges to not draw over labels, taking into account nesting and rank dir gave me an appreciation for how hard these can be, and I kinda wanted my own version (plus other features)