People find the srrangest things cute in my experience.
But yeah, clumsiness can be cute in certain contexts, but really terrifying in others.
I am a tiny bit clumsy at times.
Trip over nothing. Drop things for no reason.
But it's not that frequent, and I don't think it would come across as cute.
Me forgetting things (which is more frequent) definitely isn't amusinb
On the other hand, you'll notice extreme shyness is also often presented as cute.
(sometimes the shy character is also the clumsy one)
In reality though, anyone as shy as these characters are presented, probably has social anxiety.
And while I have found people do indeed find that somewhat cute at times, (and indeed at times it also evokes the kind of protective instincts associated with cuteness -after all, as an instinct, finding something cute is supposed to make you more inclined to look after it. That's the purpose of it in the end), as the person experiencing it, it is actually scary, and exhausting.
After all, that nervous confused reaction that some find cute is a direct result of basically operating on fear and adrenaline.
Which is, scary by definition, and stressful.
So... Some people think it's cute. Well, great. But it's little fun for the person going through it.