[ModernMech]

> After all, if you squint, ROS is a collection of things:

ROS came about because before ROS existed, robotics researchers cobbled together ad-hoc ROS-like systems using the tools you point out. ROS itself started as a project called "Switchyard", which was built to operate one of Stanford's robotics projects. Research labs around the country each had their own take on this kind of system, which made sharing research very difficult. What ROS did was standardize the platforms between all labs, enabling us to share our algorithms, which at the time mostly revolved around localization, mapping, and path planning.