There's also a reason why it's a standing goal, rather than a completed goal.
It does little or nothing really well, but it does everything kind of okay.
There's a lot of "alternatives", most of which do something much better, sometimes much much much better, than ROS, but none of which can replace it all completely. PyRobot, Viam, OROCOS, Webots, all of these do some things much better than ROS, but none of them can drop in and easily replace everything without a lot of developer time, often adding new features to the platform.