That there is a computer at ATC that a human looks at, reads what it says with their eyes, speaks those instructions over the radio in a specific protocol, anot

That there is a computer at ATC that a human looks at, reads what it says with their eyes, speaks those instructions over the radio in a specific protocol, another human listens to it (and confirms within that protocol), and inputs those control signals into the airplane. Computer -> human -> radio(spoken protocol) -> human -> plane. There aren't a lot of practical reasons it can't just be Computer -> radio(digital protocol) -> plane (There are nonzero reasons, such as the presence of weird situations, VFR aircraft, etc., but it's not a lot.)