Avengers 4: The Righting of Wrongs
Ashes to Ashes, Dust to Dust
Really though, Thanos hand selected and raised his "children". Gave them the tough love approach and figured they would live to seek his approval, even when they were mad at him for the moment, they would deep down love him unconditionally. He apparently misjudged how much he hurt Gamora and how much she resented him, as he figured his bond to her was strong enough to overcome whatever temporary emotional setback she was having. She was his favorite, so instead of continuing to restrict her and build further resentment, he would let her believe she was free, but really he was just allowing her a very very long leash. Ultimately, his goal meant more to him than his love for any 1 individual, regardless of who it was, so when he ultimately had to give up something that he loved to obtain the 1 thing that he wanted, Gamora was really his only choice.
And I get that you already understand what they were going for, you just don't buy it. and that's fine. I was feeling it. I still haven't rewatched the movie since the 1st theater opening night, but I remember how it would really attempt to play those emotional chords, that only really got me at the very end (FURY!!!!! NOOOooooOOOooOOO!!! Not Fury, man.... ;_;)
What I just read recently though, was that Hulk was misinterpreted by pretty much EVERYONE that watched the movie. Hulk got his ASS BEAT by Thanos with little effort, and was never seen again for the rest of the movie. Not even when Thanos wasn't present.
Now we all thought it was because Hulk just got a dose of "be humble, bitch, sit down". And he was so damn shook, that it didn't matter who was around, Hulk was not coming out to play. Thanos knocked the Angry out of him.... but according to the Russo's, that's not it at all.
Apparently after Ragnarok, and taking control for so long, only to get shoved in the back seat to Banner again, to be forced to come out again when it was time to fight, Hulk felt used and disrespected, like Banner only called on him when it was time to fight, like that's all he was good for. Punching ****. Lifting ****, throwing ****. He was tired of only being called upon when **** had hit the fan, and then when the **** is over, shoved back in the back seat all lonely and now one to talk to.
So speculation for the 3 movie Hulk Arc from Ragnarok -> A3 -> A4 is that Hulk and Banner will find a way to Co-Exist at the same time. Basically Professor Hulk, a smart talkative, funny yet fierce and even more dangerous Hulk
But back to Infinity War.... All I can say is they probably aren't really well versed in actual battleground confrontation, considering the world just found out about their nation, and until then, the only fighting they've done was against each other, and I'm sure it hasn't been a real all-out actual deadly war for 100's if not 1000's of years. Outside of tech development for war games and espionage reasons, I doubt they developed much in the way of open field warfare on their own territory.
But we may both just be over analyzing this movie.