I think it's a combination of the following:
- It's been 3 years since we last had an Assassin's Creed game
- It's been 8 - 9 years since we last had an Assassin's Creed ass Assassin's Creed game, meaning something that is smaller packaged, more linear, and more focused, with particular focus on assassinations (wow!) and stealth
- The setting is beautiful, golden age Baghdad. Urban parkour environment is back, though of course not on the same level as early games because this game is clobbed together using Valhalla assets. Still, the city is the star in the game and not the open ended areas like in the RPG trilogy.
- It's a very serious and intended homage to the original. Together with the obvious middle eastern setting and gameplay focus, they went ham on this. Even the robes and the overall art direction just screams old-school AC.
Personally, I think this will be a very neat love letter for its intended audience: People that miss early AC, especially my AC1 brothers. Also I really like the music.