That depends on what you mean by "repopulate the world. Do you mean with actual quests? Why not interesting NPCs that just provide fun dialogue or lore? Anyway, as long as the content was good, yes, I'd prefer a smaller game with good content over meaningless fluff. Now of course there is a point at which there is too little content, but there is a lot of room before that. I value quality over quantity. You're free to do the opposite. For example, being a completionist, I found all the crap on the various planets in Mass Effect, but that was annoying and pointless. To be fair, I doubt those "quests" took much development time and they were totally skippable.
You imply that the game consists of meaningless fluff when there are a lot of major storyline quests, plenty of companion quests, and minor story quests throughout the game.
Considering that the good quality content is still there and has not been reduced compared to its predecessors, it seems that all you are asking for is a slimmer DAI.
You are arguing that DAI should have been a smaller game, without all this extra additional (mostly) optional content that you don't need. That's cool, but what about those who enjoy this new style? Your argument is subjective. You have the right to not enjoy something. I don't like FIFA games, but I don't go around calling it a bad game, it doesn't appeal to me. That is all. DAI is a party-based narrative cinematic RPG with open world elements. It does all of that pretty well I would think.
So what to do about it?
Cutting out the fluff would make the game world relatively empty. They can make the world as beautiful and large as they want but if there is no driving force to explore a lot of their work can go unnoticed. There needs to be some filler.
Reducing the fluff could work, but considering that all side quests already cost very little in comparison to other parts of the game, I don't see how much work they can do to replace them.
In Exile suggested that the quest context be differentiated a bit more. That's fair, but it seems the context matters little to you as the "quality" remains unchanged. They are still fetch quests.
Assuming that it takes a couple of lines of dialogue, some asset design, and some inventory coding to create a fetch quest...how much can you create in lieu of it? There isn't an unlimited amount of resources.
You said it yourself. Optional content in ME took comparatively little design. Are you implying that they could have cut it out and created one quest line to replace it?
Then ME would lose its exploration aspect. What about those who enjoy it? I have a fond memory of reading about this one planet with a moon with a large rift on it rumored to have been caused by a high velocity mass effect super weapon as a last act of defiance against the reapers. Klendagon I think? I gawked at the moon in wonder. The point is that a totally random planet had something nice to explore, with the fetch quests driving me to roam the planets.