The unknowable is scary.
If you see something you don't understand, it's not a big deal. I shouldn't even have to explain this. If you want to understand, you can go and learn about it.
If you see something you can't understand, which is metaphysically immune to understanding, then yes that's a problem, now isn't it? If it's a threat, you can't defend yourself. You can't even tell if it is a threat or not.
It's crazy-making, because Turing completeness is a thing. Nothing is impossible to understand, so if you see something impossible to understand, it's like a triangle with six sides. A logical contradiction.
If a thing can touch you, if you can interact with it, then you can learn about it. Touching is knowing; something that is unknowable is untouchable. In Reality you have no need to fear the unknowable, because it cannot possibly harm you. Even recognizing an allegedly unknowable thing as different from other, knowable things is to know something about it, contradicting the premise that it is unknowable. Having given it boundaries, you can simply list the effects of things inside those boundaries. Every time it touches you, you can record what happened and when it did so, and eventually this list will become a pattern.
I shouldn't have to say but probably do: if it doesn't interact with you enough to form a pattern, then it doesn't matter if it's unknowable, because it approximately doesn't exist. Further, we can see that nothing with this sort of nature occurs in real life. While certain complex arrangements can be rare, the simple components which make them up always happen near-constantly. It's not like you can cast RPG wizard spells once every 3000 years, but not otherwise. To oversimplify, the elemental stuff happens daily or not at all.
Further, experiencing something as unknowable is something that genuinely happens to you when you have a cognitive illness. Narcissists in particular. If you see something you inherently can't understand, it is evidence that you are insane. Your genes know; you don't need to be taught. If your genes know you're suffering from a probably-fatal fitness deficit, that's a problem, now isn't it?