This is a somewhat minor point, not even related to actual movement and gameplay. But the game is quiet. Talking mainly Hardpoint here. From something like the way your commander announces things, it's missing that character. The fight. Having their portraits pop up. Them being leaders. Or the switch of command depending on where you were in the "campaign". It was a unique detail, that really made it feel like a war.
And then, there was the banter the grunts and specter would bring. Screaming, fighting, calling out enemy Titans and pilots. It brought life into the battlefield. I wasn't just playing a glorified TDM, no- this was a battle of Attrition. Everyone was fighting to the last breath, including the grunts who were dragging one another off the battlefield. They were alive. And R2 is missing that life that both the command and the grunts brought.