Here is an extremely intelligent critique on the successes and missteps of Dragon Age: Inquisition. I agree with almost everything he says.
https://www.youtube.com/watch?v=UMFnSqfhdKw
Overall, I think the game was a success. Sure, it was flawed and definitely could have been better in many regards but the game has many qualities. Despite it being a good game and GOTY, I don't think it's going to be a classic rather I think it will be remembered as a good game with some flaws.
I think its biggest strength was how it handled religion in a world full of magic and the supernatural. It doesn't matter if the Maker exists or not, what matters is that people believe in the Maker and they believe that you are the Herald. I personally didn't think I was the herald but I used the Inquisition's belief in the name of good and in the final moments of the game I even asked myself if there really wasn't a Maker. There were too many coincidences, imo. Why exactly were you at the right place at the right time when you got your powers? Maybe the Maker works in more subtle ways. In the end though, it doesn't matter if the Maker exists, what matters is that people believe in him and that belief alone has the power to drive people to do unbelievable acts of heroism (and cruelty) and to make the believer's life more meaningful. It would be interesting if BioWare ever made an atheist Divine who while does not believe in the Maker sees the potential (and need) for people to believe.
As far as companions go, they were a mixed bag for me. On one hand I really liked Cassandra, Vivienne, Dorian, Solas and Cole while I thought the others were kinda meh...there was something strangely missing and I think I know what it was . There is no character that acts as a counterpoint in Inquisition. Everyone basically agrees with you. Morrigan and Sten (and to some extent Zevran and Shale) challenged your ideas and your perception of the world and were not afraid to call you an idiot when they disagreed. There needed to be more contrast in the roster. That is why I also love Athelstan in Vikings so much, among all the bloodthirsty warriors he is the only rational guy there, he serves as a counterpoint and that is something DA:I needed.
The gameplay is definitely the weakest part of the game. There is a ton of content in the game but unfortunately it is spread too thin. There are not very many interesting side quests, which is a real shame. It really does feel like The Old Republic 2.0. Worst yet, the side quests hurt the tempo of the game. The interesting parts are really stretched out because of this.