Imo, ME 2's Suicide Mission was the best final act of the entire trilogy hands down. There wasn't a 'pick your 2 favorite squadmates and leave the rest behind to hang out on the Normandy and reappear in the final cutscenes' moment. Every squadmate had a hand in the final act. Why Bioware abandoned this in ME 3 is beyond me.
Loyalty missions added depth to ME 2 and made me feel like Captain Kirk getting to know each squadmate as an individual instead of reading about their background in a codex entry. ME 4 does not have to follow the same exact formula of 'comforting your crew'. What ME 4 SHOULD do is look at the strengths of its predecessors and incorporate that into the story.
One of the main reasons why The Hinterlands in DAI becomes such a drag is not because it's a massive area. It's because the majority of your time is spent you're running around, doing pointless fetch quests that add nothing to the story except maybe a weapon or armor that you will soon not need once you start crafting better gear. Deliver a potion, kill x amount of rams, find a landmark, all to gain experience points. Since I'm leveling up, I might as well have a reason to actually give a damn about the mission. Even if it's a skippable mission that is not part of the main story, doing it could affect the outcome of the main plot.
And who says, ME 4's loyalty missions have to unlock a squadmate's bonus power this time around? They can simply be just that. Loyalty missions where the end result would be squadmates being more willing to suspend their personal feelings about your in-game decisions, and have your back no matter what you decide. Since decision making, or the illusion of choice, is what made ME games stand out, I don't see how loyalty missions could be a bad thing this time around.