It's not that there is anything wrong with it. It's that it has limits. Set your RTH altitude too low and you risk the craft running into something on it's return (OA is not perfect), and if you're just chilling out waiting for it to show up chances are it's going to hit whatever it was flying towards before you can react, or having OA get a false positive due to the Mavics sensitivity to sun and bright reflections and have it start heading for the stratosphere till the battery level runs low and it just lands itself wherever it happens to be rather than coming back. (yes, OA appears to override altitude limits).
On the other hand if you're monitoring RTH closely to avoid these issues I find it more engaging to just fly the craft back.
It's really important to consider anything the craft is going to do "automatically" on your behalf, including landing! Set RTH for 60 meters to clear trees and if you happen to be flying with obstructions overhead (trees, bridges, power lines, etc) at the moment it gets triggered you will have to react fast to avoid a crash induced by it. Some folks like to use it a lot, others not as much. There is no right or wrong to that decision, just right or wrong to how it is set, and you can't just set it and forget it. Each flight should include checking how it is set before depending on it to not cause you grief if/when activated.