Ah yes...subverting expectations. Because it worked so well for the Star Wars franchise. Killing Thanos in the beginning, took away any real over-arching threat from the film IMO. Without Thanos, the film has no antagonist. There's no real conflict. So the Russos just filled up the movie with lots of jokes. A better approach to subverting our expectations would've been if they had setup this big fight with Thanos, making us think they're going to win since Captain Marvel was there. She could've been overconfident only to have them lose because he still possesses the Infinity Stones. It would've been a great way to setup a weakness for Captain Marvel and also a character arc of using teamwork. Thanos, almost beaten could've escaped using the Space Stone. Now that he knows the Avengers are looking for him, he gathers an army to battle them.