I've been a ROS 1 (and now 2) user since 2010. I like the game engine analogy given elsewhere in the thread, in that ROS gives you some important things "for free" if you cooperate with its ecosystem conventions. Data bagging, visualization, teleop, and sim are the some obvious ones that I think a lot of teams don't think about if they're just focused on getting cartographer or whatever going, and not considering the larger development and debugging questions.

For some, packaging/deployment would also fall under the umbrella of a solved-by-ROS problem, however I don't think the Open Robotics supplied debs are suitable for most product deployments, for a variety of reasons that I've discussed in two separate ROSCon talks.