Some of the players in my game have expressed interest in having critical failures in the game. I will admit it is fun when the enemy rolls a natural one and things go hilariously bad for them, but the fact is that critical failures are far more devastating to player characters than to monsters.
I'm glad you see that. Most players don't.
But "fumble on a 1" is both a terrible mechanic and an unessential one. I don't know where this house rule for "Fumble on a 1" came from, because published fumble systems - including the infamous "Good hits and bad misses" back in the day - never worked like that.
The first thing you have to do is add a fumble confirmation roll of some sort that alters the probability of failure so that the better you are, the less often you fail. For example, a typical fumble confirmation roll would be "Roll again. If you miss again, it's a fumble."
With that change alone, hopefully you can see that the dynamic changes greatly. If a character needs a 20 to hit, then almost every 1 will result in a fumble. But if a character needs a 2 to hit, then they must roll a 1 twice in a row to fumble.
There are a bunch of other options as well. For example you could on a threat to fumble have the confirmation roll be a random skill or ability check like, "Make a balance check. If you fail by more than 5, you suffer a fumble." or "Make a DC 5 Constitution save. If you fail, you suffer a fumble." With mechanics like that skillful players might never or almost never fail. After all, there is no necessity that you automatically fail on a one for every sort of roll. With a skill check, a high level character might never fail to hit the target number, and in 5e players might have proficiency on checks and so need two terrible throws to fail.
The point is a confirmation roll that is harder and harder to fail the more skilled the combatant, whatever that roll is, more than offsets against multiple attacks when designed properly.
The other thing that I see in badly designed fumble systems is that they tend to have tables that produce lots of outrageous results. So instead of something like, "Weapon takes 3d6 damage" or "Opponent gets a free attack on your weapon", they have something like, "Weapon breaks." The later is really silly (and frustrating) when the weapon is a +5 adamantium weapon that just shouldn't break easily. Or they might have "Critical hit self.", rather than something like, "Make an attack on yourself. You have disadvantage when dealing damage, and do not add your strength bonus to the attack. You may ignore this result if you are using a natural weapon." Fumbles can even be minor annoyances that still realistically add color to the combat like, "Your footing slips and you are off balance. Your opponents have advantage when attacking you the next round.", or "Your attack leaves you off balance. If you are using a shield, you cannot use your shield to defend yourself during the next round.", or something like, "You overextend on your attack, leaving yourself exposed. The enemy you last attacked may make an additional attack against you without spending an action, but they have disadvantage on the attack." Fumbles don't have to be outrageous. They just need to help you concretely imagine things that could be happening in D&D's otherwise abstract combat system.
