EDIT: I remember being amazed when Go came out circa 2011 that I could just "go build" a project and it just worked. One had to understand "GOPATH" which was slightly counterintuitive but not too bad, and of course it wasn't reproducible (both of those problems are pretty much addressed nowadays via modules), but I was blown away that I could actually just "go build" or "go test" and focus on my application code instead of my project tooling.