The tyranny lead by reasonable people like Irving, Gregoire, and that Templar guy who let Finn basically wonder around Ferelden unsupervised, and lets mages learn magic taught by learned teachers with tons of books on the subject, even though they probably shouldn't even be letting them know anything about magic.
And it's all free, I might add, not even nobles get free room and board, food and education.
Basically a Soviet gulag.
I notice how people gloss over the toxic conditions of the Circles of Magi and act as though the mages should be grateful for being forced into servitude to the Chantry and their militant arm.
It's not as though the Chantry controlled Circle is some idyllic paradise. The Starkhaven mages note that the Circle of Starkhaven was bad, and some of the ones we encounter have been driven to the brink of insanity; Karl was writing to Anders about the horrors of the Circle of Kirkwall, which prompted Anders to leave Ferelden for the Free Marches, to rescue his former lover; there were mages who were beaten, whipped, tortured, raped, and made tranquil. The frightening power that the templars had over mages lead to these abuses.
Even in the Circle of Ferelden, the mage protagonist can address that the Circle is "an oppressive place", and Wynne will argue that the protagonist can return to the Circle and change this as a leader of the mages. Aneirin was hunted down and nearly killed by the templars as a young boy for running away. Even Irving notes that the environment of the Circle is one of survival, saying to the mage protagonist: "If you want to survive, you must learn the rules and realize that sometimes, sacrifices are necessary." The First Enchanter also admits: "And Chantry and templars are models of magnanimity? They would make us all Tranquil if they could, and call it a kindness. They fancy themselves our guardians, sitting smugly on their righteousness."
It's not too difficult to see why some see the Chantry controlled Circles as tyranny.