Birnin Zana
Honorary Wakandan
The lore, as in; Reapers, extinction cycle, Catalyst, Protheans, etc, etc.
As opposed to just running up in the Citadel (with 2 other teammates--I hated all those DLCs where you were fighting solo or with one teammate) killing or controlling the Reapers and make the rest of the game about the characters--like the whole series is about--and the post Reaper War world. I would have like them teasing intergalactic imbalance.
If it was about the lore, that was a really bad way to go about it. I was very familiar with the lore when I initially finished and even I was confused about what exactly was happening and how / why it went down.
Indeed, if they went about it the way you mentioned on your second paragraph, and included EMS to help shape how successful or unsuccessful you would be in achieving the goal, there would be little to no complaints. Instead, they went with the smart-dumb approach.