I'll be seeing this again soon, but I've been thinking about how arbitrarily the characters were used in the climax. We didn't see their character or skill sets come together in a compelling way to overcome all odds. It could have been ANYONE dying while trying to plug a cord in. Or toggle a switch. I think it was a factor in why their deaths felt so hollow. As was said above, it was plot over character.
The heavy should have gone down while providing cover for the others, get the pilot into a stolen Tie, etc. Those are on the nose examples, but I didn't feel like their actions or fates fell in line with their characters. That's something The Force Awakens got right, where everything that happens on Starkiller was a function of character; Han trying to save Ben, who turns on him. Chewie going postal after his death. Kylo's beef with Finn, who faces his fears to defend his friend. Rey taking up the saber. It all flowed from character, and those moments hit home as a result. In Rogue One, they land on the base and nearly all turned into plot cogs. The only death that flowed from character was the robot, which was why it was the only one I cared about.