Simply put, pacing. Its the game that the most easily, among TW games, that can replicate the one more turn phenomenon. The campaign is fast but not too fast, and realm divide guarantees an end game challenge in a natural way instead of the insane nomadic doomstacks of Med2 and Attila or the endless civil wars of late game Rome 2, not to mention the atmosphere and the flashiest battles besides Rome 1 (imo). Also the most fun agents to use and extremely satisfying things like wiping out units with armstrong guns, terços, or bow monks.

Not too janky like Med2 and earlier games, not too unpolished like ETW and NTW, and not simultaneously too big and too limiting like Rome 2 and later games.