Yes, it's "fine." But there's plenty of room for something more interesting than just "you miss." Half your rolls are going to be misses; why not make that 5% of the time that you roll a nat-1 into something a little more interesting?
Because it's triggered by the thing your character is supposed to do in combat (attack), and you have no control over when it happens. So it isn't interesting, it's just arbitrary punishment. Crits are an equally arbitrary reward, and that is why they are just a modest damage boost--not much better than a good damage roll on a normal hit.
It's the converse of a critical hit. A nat-20 is already an automatic hit; why wasn't that "fine as is"?
Crits are bad game design, but they give players a moment of "Yay, I got a 20!" That little burst of excitement is their sole function and the only justification for having them. I see no reason to adopt bad design for the sole function of providing a burst of disappointment.
Other options: "You open your defenses, your foe gets an immediate AoO on you". "Your weapon breaks (it gets a save if magic)". "You are blinded for the next round" (could be spashed mud, a slipped helmet, glanced into the sun - loads of ways to narrate this). "You lose your next attack". "You cannot move more than five feet next round".
If you make three attacks per round, which is fairly common past 5th level (dual wielder, monk, Polearm Master, berserker frenzying), you are going to hit a natural 1 about one round out of seven. If we figure a typical fight is 3-4 rounds, that's every other combat.
The OA doesn't seem
too bad, except that it punishes melee warriors for being melee warriors. Losing your next attack is fine in theory but in practice raises the question of how long you have the "no attack" penalty hanging over your head, and encourages weird behavior to "use up" the lost attack. The other two? You break a weapon every other fight? What are you wielding, styrofoam? You spend 1 round out of 7 blind or stuck in place?
I stand by my position: Fumble rules as commonly implemented lead to slapstick absurdity, and it's quite hard to come up with a non-silly implementation. There's a reason no edition of D&D has ever had them.