Like many other seasoned AC players Mirage was so disappointing.
Valhalla was too big but the story was relatively captivating. Mirage is the complete opposite, boring pointless story with a terrible ending and a tiny weeny map. Only took me 1 week complete the game (and I work full time).
Lack of skill upgrade abilities (valhalla had too many). Gameplay was dire, so clunky, awful combat, too difficult to run away. Tool upgrades were mostly useless and unable to carry enough throwing knives etc. The climbing ability was absolutely shocking, chests far too difficult and annoying to get to and often rubbish gains.
I'll seriously think twice about buying the next AC game after this.