Most other flight automation apps that use the DJI SDK upload missions to the drone for execution. This approach is called onboard waypoints, and it is the reason why these apps are essentially clones of each other - they rely on the same underlying flight controller. Furthermore, onboard waypoints only offer a very specific, limited command set and DJI rarely updates this command set. DJI has also excluded onboard waypoints from certain drones, such as the Mavic Mini and Mavic Air 2, meaning many apps cannot support those drones.
Dronelink uses a different approach called virtual stick, which means Dronelink is actually a custom flight controller sending stick commands in real-time as a human pilot would using a remote control. Many of the features available in the Dronelink mission planner, such as the Facade component type, lists of commands (drone, camera, gimbal, etc), or even chaining multiple component types together in one mission, can only be achieved by using this approach (learn more). Not only does the team behind Dronelink have the most experience with this approach to flight automation, but they also have the most experience with creating apps for the DJI SDK in general (learn more).