No one said Vivienne was handed the position for free, or was noble/something else to be entitled to it.
They said that people who achieved something in life, even through blood and tears, can very well forget what it was like before, and all the injustice they faced as well, so they can be smug to those beneath them in position.
They can become more interested in keeping their earned position, rather than dealing with the injustice for anyone else.
And that's where you get Vivienne. What she says is essentially right, that was the worst time for rebellion, it's something that should have happened(the negotiations for change, not the rebellion), a long time ago. Although she didn't say it like that, she was more pointing out that everyone besides her is selfish.
But you can see that she is smug, and believes anyone that wants their freedom is a selfish brat, that can't appreciate what was handed to them. That is what makes people believe she's full of it.
So people have argued that she is equally selfish. She lost her position of power and influence, no matter how she got it, and she's pissed about that, not the Circle system vanishing being worse at this point. It's awfully tempting to think that, especially when we find her in Inquisition, the new rising power.
This is all speculation, but what did you expect to hear from a pro-circle Mage? People that are pro-Templar, will find truth in her words, because beneath the smug hypocrisy, she does make a point. People that are pro-Mage, will be able to also see that smugness and point out that she lacks the understanding of how things came to this, which she does lack.
So, we have some indications that Vivienne actually wants power. She was First Enchanter and influence to the nobles. She is now, in Inquisition, a new rising power.
Is she here, because she wants to set things right? Or does she only want power, for herself, and will support anything that promotes that?
I don't know, but i want to see, she is actually a very interesting character with lots of potential.
Also, remember that the Mage-Templar conflict does not have an easy way out. Arguments are solid for each side. Vivienne is not right, or wrong. She just sees things from her perspective.