A lot of the game is centered around your crit %. Crit upgrades tend to be behind sizable SP checkpoints, at many stages of the game: critical culling early on, divinities like hyper critical later, gear upgrades.
However, there is no "exciting" indicator that crits have happened. Other games change the color of the damage, or size of the damage font on a successful Critical hit. While there's no damage on screen for idle slayer, maybe some sort of "Crit" Indicator could be used, on a successful critical hit? As it stands, getting upgrades that increase your Crit chance feels forgettable, even when the extra SP should be the main selling point.