Many people think that is not possible to create AAA game with Unity, so they choose Unreal or Cryengine.
But what defines AAA game - graphics quality, hardcore features - nope.
Probably first thing - money. If you have no budget you can forget about AAA.
Next thing - size. You can't create small mobile look AAA game. So does Unity restrict you to make big games - no. You can make as much levels and worlds as it possible. Next thing - atmosphere: if you have lame designers you can't do AAA things in Unity or Unreal or Cryengine at all and it is not a problem of engine - it is a problem of people. Next thing story - with high budget storywriters you can do magic and even not well done games can be hits: like Witcther 1 or modern Life is Strange. Awesome music it is also the part of the game.
I'm not telling that Unity have no limitations. For example huge open worlds it is not what Unity doing well. For such games Cryengine is better for now. So with small limitation it is absolutely possible.
So why there is no AAA game on Unity. Because of lack of experience. Unity is easy to start game engine, so many beginners start to use it, doing shit and say that its a fail of engine. They disappoint and start other engines. Also they forget that time is passing and their skill is growing up. So they make their AAA game at age of 30 as it should be.