When nearly the entire world does it, it becomes something you can't ignore.
What someone intends and what someone does can be two different things. Like for example I'm sure you are intending to have a constructive discussion, but what you are doing is being a condescending jerk.
The length of the main story compared to the length of the game overall has nothing to with the protagonist. It has to do with the plot. Even with a set protagonist, the story would have been the same length.
You are playing a role: the role of the Inquisitor. The story of the plot itself is what supports you.
Commander Shepard could have no past whatsoever and the plot of the Mass Effect trilogy wouldn't be affected in the slightest.
Lmao first of all you have seen nothing of "nearly the entire world" so don't talk rubbish and grow up. Because if you cannot learn to ignore that which annoys you then you will be eaten alive by bitterness and depression. And that is a fact my friend.
intention and outcome has nothing to do with what I said lol.
The lack of plot shows the lack of details intended which also means the details intended for the character also.
you got half a character and half a plot and you say that is good because you have the freedom of headcanon?
Ok so answer this...
When DA4 comes out and destroys your headcanon what then?
It's the same reason they cannot do a ME game set after Shepard because it means the freedom of choice would have to be taken away and 2 3rds will be made out to be wrong with what they believe happened.
Headcanon would be the same problem.
No you are playing the role of someone imprisoned and falsely accused who is suffering memory loss and is SET to become the Inquisitor.
Just like you can try and be anti Andraste but at some point without your say so your character will say "I am the Herald of Andraste"
It kinda ruins the headcanon right? 
Anything I said you don't like or don't know how to answer just ignore and that can be your first lesson in learning how 