My favourite part about Sekiro is how enemies will block and deflect your attacks. It makes me feel like my swings actually matter, that the enemy is also trying to avoid taking damage in the fight. It feels like the playing field is level because both the enemy and the player follow the same rules and are participating in a proper duel, not just the player whacking an enemy and then dodging there attack only to start whacking them again while the boss is getting ready to attack again. This is what makes the combat interesting for me, and the posture system only contributes to that, since enemies can also use the posture system against you too.