I managed to type out what about Arrival made me go WTF!!?
It's the ending, and it makes no sense.
short and confusing version:
It does not make sense that you can do something in the past to create a situation in the future (the meeting), but it's the situation in the future where you are told that it was what you did in the past that caused the meeting. And you were not even given the info you used in the past to cause the meeting until it was given to you at the meeting in the future so that you could go back to the present(past) and use it to as a reason to cause the meeting(in the future) at which you were given the info you used to get the meeting.
I simply can't wrap my brain around how that makes any sense at all.
longer version:
basically, to stop a nuclear attack against the aliens, Amy Adams has to call the Chinese General on his private phone.... a phone to which she nor anyone she knows, knows the number to. so she glimpses to the future, because Alien Universal language taught her that time is non-linear... but when she glimpses to the future, it's not to how she discovered the generals private number so she could call him, it to when she meets the general, after she called him, and he's happy to meet her because she called him. Now he is explaining that he only met with her because she called him on his private phone (to which he pulls out his phone and shows her the number.... yes that's how she got the number, he gave it to her after she supposedly called him on it. :/) and told him his wifes dying or last words (to which he also told her this as well in this moment... right after giving her the phone number). He states that had it not been for those 2 things, he wouldn't have ever spoken to her, nor taken her seriously. So now that he gave her what she needs to cause the meeting that they are already at, she now snaps back to the present to call the Chinese General on his private phone, tell him his wifes dying words and talk him out of attacking the aliens w/ nukes. This lead to a worldwide unification, and caused the general to be eager to meet Amy Adams in person, where he will now tell her that he only took her call because it came on his private line, that she didn't know until he shows it to her on his phone *right now*, and because she told him his wife's dying words, which he also then tells her *right now*.... WTF is this nonsense!?
But yes, this movie was also pretty dull to be quite honest. Interesting (until the ending), but dull.