The casting cost pushes it out of the competitive zone, even factoring in lesson/learn, but it can work with commanders like Iroh, Grand Lotus or Zhulodok, Void Gorger
Technically Treasonous Ogre too, but dethrone just doesnt matter on that card
Because Breena is so efficient at loading up on +1/+1 counters I've leaned into it with a strong counter subtheme: we use those counters to draw cards off Dusk Legion Duelist, ramp with Scholar of New Horizons, have board wipe insurance with Felisa, Fang of Silverquill, and turn our team into lethal angels with Sigarda's Summons
Additionally, decks with their own alternate win conditon, like combo decks or Toxic strategies that win by giving players poison counters, can be less vulnerable to Exile effects by including more instants and sorceries and fewer permanents
Cassius Jr., of course, was the victor