um.... critical failures can occur on any roll, but I have 2 complaints with them....
They happen WAY too often
They have no additional negative impact, like fumbling at attack to disarm yourself or injure yourself, failing a lockpick so bad it breaks the lockpick and/or jams the lock. Even so that if you critically fail a saving throw you suffer disadvatage on your next action / knocked down additionally, whatever is most appropriate.
Now I realize a lot of these negative impacts are DM discretion, so the game might just be being lenient on 1's... and it's seriously not something that needs to be implemented now as it's more of a flavour thing, but critical failures are able to occur on any roll other than damage.
