The problem with your point, Tom, is that even saying your decisions in previous games pay off across the entire game is, well, moderately true at best. If I killed off the Rachni queen in ME1, the Rachni still come back under Reaper control. If Mordin died in ME2 (which was relatively more common than losing others due to the fact that he was the most fragile member of the crew, I think), does the genophage mission play out much differently, or is there just a not-Mordin there? What about if you killed Wrex? Do the krogan still help the Turians out?
Now, I understand that there’s limitations here – if you have to account for every possibility, then your development cost starts getting to be ludicrous. For me, where I was the paragon of paragons and tried to save everyone, let the Rachni go, etc, etc, the story did reflect a lot of my choices because almost every mission ended up involving someone I cared about, which really made my decisions stand out – and that’s great. Someone who was more ruthless though might be a little put out though that killing the Rachni queen didn’t get them anything, or that destroying the genophage cure data didn’t seem to matter. The one place where it does pay off, and where I was both pleasantly surprised and mildly annoyed at my choices, was with the quarians and the geth – if you had simply destroyed the heretics instead of reprogramming them, getting the geth and quarians to cooperate is actually much easier (but it does make the geth weaker in terms of war assets). More things like that would really have helped the game.
However, I don’t think it would have been that hard to make the game take into account more of your actions, but ironically, I think the easiest place to have taken those actions into account would have been the ending, in a single long conversation with Harbinger or whatever. If you do that, you only have to rewrite that one ending and instead of people getting soured on the rest of the game, everyone looks back on the rest of the game and goes “huh, I guess that stuff mattered more than it seemed.” The problem is that now, from basically the time you leave Anderson’s camp to the end of the final cutscene, the only difference, and your only agency in the game, is which cutscene you want to see at the end.
Think about the first game. You go to Ilos, jump through the Conduit, and you get to choose whether the Council lives or dies (which sure seemed like a big choice). You beat fight your way up through the Citadel and then you have a conversation with Saren, and it is possible to get him to kill himself; even if you don’t at least you get to confront him. Then you beat Sovereign-possessed Saren and you get a nice bit of denouement where you pick humanity’s first representative on the Council. That’s some fairly strong stuff there. Even just in terms of exposition, I think the conversation with Vigil is still one of the most heartrending scenes in almost any game I’ve played.
Now let’s look at the second game. As soon as you hit the Omega 4 relay, your choices in the rest of the game start to pay off. If you didn’t have the shields, or the guns, or the new armor, pow, people die. Then you have to decide who does what on the Collector base – choose poorly, and bam, someone dies. If you don’t have people’s loyalty? Bam, more people dying because of your choices. Then, you beat the stupid terminator baby and you get to choose whether to destroy the Collector base or not (another choice that seemed pretty major at the time but which doesn’t pay off either way in ME3).
Now let’s look at ME3. From the time you leave Anderson’s camp, the only thing you get to make any decisions in is the conversation with Anderson and the Illusive Man on the Citadel (still not quite sure how either of them got there, honestly) which happens while you are literally being mind controlled by the Illusive Man, and ultimately has little relevance on the ending as far as I can tell. Then you get your conversation with the deus ex machina and pick your cutscene. That’s it.
