Holy shit, I managed to find it (I read it many years ago). Having good Google fu feels like magic at times; "sci fi novel humans missed technology breakthrough".

Harry Turtledove; https://en.wikipedia.org/wiki/The_Road_Not_Taken_(short_stor...

"The Road Not Taken", a short story by Harry Turtledove.

https://eyeofmidas.com/scifi/Turtledove_RoadNotTaken.pdf