One problem of scale here is that unless a tooling investment has made literally 100% of the work easy, most of a developer's workweek almost by definition wind

One problem of scale here is that unless a tooling investment has made literally 100% of the work easy, most of a developer's workweek almost by definition winds up spent on the remaining slow and hard problems. So investing in tooling certainly improves productivity, but whether it can make things "fun" depends on which categories of hard/slow problems a given developer enjoys.