Very simplistic description: The term rotation originally comes from games like Overwatch and LOL that have teams that play together, heading towards a particular place. It was meant more literally, often turning at a corner in a strategic, disciplined formation. Now it generally just means movement from one place on a map to another in general. Since Apex doesn't have "objectives," except for needing to move with the movements of the ring, it comes off a a bit of a weird term, but is used thusly nonetheless.
I feel like if lots of people started playing Newcastle effectively, we'd see casual players calling for a nerf due to his very effective revive capabilities, much like was the case for LL when she had the shield.