The Quill realising Gamora was dead... then immediately doing the worst thing possible to avenge her by helping Thanos to live made no sense. Also the fact that not one of multiple superheroes didn't just knock him over the head. THe only person that needed to actively keep doing what they were doing was Mantis, everyone else could afford to stop and punch Quill in the face. IT was such a cheap crappy plot device.
Also as higher up, yeah, Hulk in the suit was horrible CGI.
My biggest issue was the whole we must keep them away from Vision... then they all basically ignored Vision and a bunch of people who can fly or move really fast took ages to get over there.
THe overall fight at the end was stupid in that, they had a shield and we know they have ships, why didn't they send ships to bomb them while massed outside the shield with ease. Why not open the shield and have War Machine drop his bombs in the same way.
THen when Thor arrives rather than target the two super villians and despite his ability to crush every bad guy around him in seconds somehow he focuses on the little guys, doesn't kill the two bigger bad guys right in front of him and instead ignored them entirely, then he went to kill drop ships as they try to escape rather than protecting Vision which should be his only goal. Every single little bad dude could have killed everyone in Wakanda, Vision and the last infinity stone were the only thing that mattered at all.
It's still a good film but a few too many things took the easy/stupid plot option to get around and just a tiny bit of change could have made the film near enough to a perfect super hero film.