If you played DAO, especially if you played it multiple times, like as a dwarf noble, human noble, mage, etc, then you experienced a long introduction unique for any type of character you created. Take dwarf noble for example, a couple hours before the game really starts you are playing your 'origin' story. All choices have consequences and visual results. Before the game starts you choices as dwarf noble determine what happens with your brother, how other dwarves will view you, you have so many options you must reply a few times as dwarf noble alone to see all the variety of outcomes for the many choices. For example at the feast do you support the land dwarves, or embarrass the noble pushing for that because his true motivation may be to get money, or challenge to a death duel, (3 different outcomes on that one little thing there), how your conversations go effect if you find your brother murdered or you fight him, many dialogue changes depending on things you said or what you did at the proving grounds, etc. This is just a beginning story that nobody ever will see if they didn't play dwarf noble, then there are a ton of other beginning stories for each option. All of this is nixed in DAI, you begin the same no matter what you select, so nothing different.
In DAO, you are eager to return to your 'origin' area to address what disaster happened and also how various characters you interacted with during that origin story will react to you when you revisit them.
In DAO, you see results for most of your side quests. In DAI many are fetch or find a letter with the last wish of a dead person and fulfill their last wish without ever talking to an NPC by fetching and dropping something.
In DAO, all the zones had a deep story with it's own problems and villians. The circle tower do you side w/ templars or help mages, and the possible outcomes. In orizzmar who do you support as king, then with blanca do you support her or the golem, if blanca do you talk her out of making golems or support making them, etc. In Redcliffe the possessed brat and how do you resolve that or do you just leave and let the city get destroyed, if you solve that area do you sacrifice queen, save everybody, who do you send in the fade to help him, do you make a deal w/ the demon or not? AND all of these choices show long term outcomes in the end game slides. IN DAI - you are doing some quests in the other zones but you don't even know if you beat or fixed the area or not, not much of a story, mostly claim areas and if you run out of things to do you assume it's done, no end game slides on helping the area and in the side zones no choices, you either help them or don't.
In DAO you must get allies and visit the zones for your battles, if you don't get allies then on the final battle scenes you don't have them. If you do you can summon them to help. In DAI, you never use your allies, no end game slides either for getting or not getting them.
DAO expansion w/ being able to customize the keep and upgrade it was more interactive then DAI. Were you excited in DAI how the chantry or garden look identical and the difference being 2 or 6 potable plants? Or the tower upgrade only being either templar or mage NPCS inside the back tower? The keep not being used for anything?
I don't understand how so many love DAI UNLESS you didn't play DAO, then I understand completely. If you played DAO and on biowares promises that DAI would be going back to its roots and being like DAO but better, you'd be pissed off they lied.
I could go on further but find it funny people think negative reviews are just trolls, must be that DAI got a lot of first time sales and since most console games don't have much substance, they are mostly action/fight, nobody knows any better.