The Robot Operating System is an open-source project that is essentially middleware between Linux, sensors, actuators and algorithms. Its purpose is to facilitate the design, debugging and operation of software for robots. If you want to move away from amateur-hour spaghetti code and create software you can build upon, robot after robot, then a middleware (or framework) like ROS is an absolute necessity. That is not open to debate outside the confine of YouTube commenteers who’ve never built a robot or programmed anything more complex than a pocket calculator. You don’t want to be that guy.