No thanks. I want my heroes to be heroes, not butter-fingered buffoons who can't go a single combat without accidentally taking out their buddy.
It also greatly penalizes classes that have multiple attacks per round while having little impact on magic users and rogues.
I do a couple of things to try and combat this:
1: Critical hits/fumbles also apply to any spell attack and saving throw. So a creature that rolls a natural 20 has a chance to in a sense cause the spell caster to fumble. A creature that rolls a natural 1 in a sense allows for the spellcaster to crit with their spell.
2: I continue to utilize the 3e/3.5 rule of Confirming the Crit/Fumble. Rolling a natural 1 or natural 20 is not enough. If a player rolls a natural 1, they make the attack again. If the attack misses, then they are considered to have fumbled. Makes fumbles more rare. Likewise, on a natural 20, even if the player misses to confirm, I still give them max damage on their attack so that it continues to mean something, even if they don't get double damage (actually double max damage in my games) or roll on the critical hit chart I have.
As for the tables I use, this is what I present to my players:
Critical Hit Table
1-5-Target is knocked prone.
6-10-Target is pushed back 10'
11-15-Target is disarmed, weapon knocked 10’ away in a random direction.
16-20-Target is pushed back 10' and knocked prone
21-25-Target is pushed 10' and disarmed.
26-30-Target is knocked prone and disarmed.
31-35-Target is pushed 10', knocked prone, and disarmed.
36-40-Target moves at half speed until magically healed or DC 15 Medicine Check
41-45-Target immobilized until the end of their next turn
46-50-Target is limited to either a move action, bonus action, or standard action for 1d4 turns.
51-55-Target takes a level of exhaustion
56-60-Target takes 1d6 bleed damage at the start of their turn until magically healed or DC 15 Medicine Check
61-65-Target stunned until end of their next turn.
66-70-Target blinded until magically healed or DC 15 Medicine Check
71-75-Target takes additional 1d8 damage anytime they take damage until they get a long rest
76-80-Target only regains half what they normally would when receiving magical healing or using hit dice to heal. Lasts for 1d4 days.
81-85-Target has the poisoned condition. At the end of each turn, they can attempt a DC 20 Con save to end it.
86-90-Target takes damage, and one adjacent enemy takes single max damage (if no adjacent enemy, reroll)
91-95-Target takes triple max damage.
96-97 - Secret Achievement. Must roll a 96 or 97 after confirming a critical to find out.
98 - Secret Achievement. Must roll a 98 after confirming a critical to find out.
99 - Secret Achievement. Must roll a 99 after confirming a critical to find out.
100 - Secret Achievement. Must roll a 100 after confirming a critical to find out.
Critical Fumble Table
1-5-Attacker is knocked prone.
6-10-Attacker stumbles and moves 10' (this movement provokes attacks of opportunity)
11-15-Attacker is disarmed, weapon knocked 10’ away in a random direction.
16-20-Attacker stumbles and moves 10' and knocked prone. (this movement provokes attacks of opportunity)
21-25-Attacker stumbles and moves 10' and disarmed. (this movement provokes attacks of opportunity)
26-30-Attacker is knocked prone and disarmed.
31-35-Attacker stumbles and moves 10', knocked prone, and disarmed. (this movement provokes attacks of opportunity)
36-40-Attacker moves at half speed until magically healed or DC 15 Medicine Check
41-45-Attacker immobilized until the end of their next turn
46-50-Attacker is limited to either a move action, bonus action, or standard action for 1d4 turns.
51-55-Attacker takes a level of exhaustion
56-60-Attacker takes 1d6 bleed damage at the start of their turn until magically healed or DC 15 Medicine Check
61-65-Attacker stunned until end of their next turn.
66-70-Attacker blinded until magically healed or DC 15 Medicine Check
71-75-Attacker takes additional 1d8 damage anytime they take damage until they get a long rest
76-80-Attacker takes weapon damage.
81-85-Attacker takes max weapon damage.
86-90-Attacker takes max damage, and one adjacent ally takes weapon damage
91-95-Attacker takes double max damage.
96-97 - Secret Achievement. Must roll a 96 or 97 after confirming a critical to find out.
98 - Secret Achievement. Must roll a 98 after confirming a critical to find out.
99 - Secret Achievement. Must roll a 99 after confirming a critical to find out.
100 - Secret Achievement. Must roll a 100 after confirming a critical to find out.