The problem with "Arrival" is that it's based on a huge plot hole and the story just makes no sense.
The Reapers always hide their existence. They try to eliminate all evidence of the cullings so that no one can ever be prepared for it. Heck, a large part of the first game was about Saren trying to prevent Shepard from uncovering the secret of the Prothean Beacons and learning about the Reapers. In fact, without the Prothean warning, no one would know that the Reapers existed.
So why would the Reapers intentionally leave behind an artifact that not only reveals their existence but also gives information on their secret invasion plan? It just makes no sense and runs completely counter to their goals.
The character motivations also make no sense. So Dr. Kenson has been indoctrinated and wants the Reapers to come through and conquer the galaxy. Then why did she reveal that secret to Shepard, someone she knows will try to stop her? Why not just stall Shepard for the two days it would take for the Reapers to come through and then try to indoctrinate Shepard after the Reapers have arrived? Considering how everyone on the asteroid had been indoctrinated, why didn't they work to dismantle the thrusters to prevent the risk of the Alpha Relay from being destroyed?
I think the biggest problem with everything in Mass Effect starting with "The Arrival" is that they emphasized emotions at the expense of logic. They basically wrote the game to make the audience feel certain things but just didn't care if it actually made sense or is consistent with previous lore.
