That's rather trite, especially considering it follows that standard wise-mystic pattern of "two statements which contradict each other." Someone wrote a comic about it but unfortunately I can't find it.

There's nothing inherently contradictory about an unknowable truth. Disagree: it's merely trite, not incorrect, and in spite of being trite it still brings a grin to my lips.

Is it a mistake to say "There may be an ultimate answer, but we have no means of reaching it"?

I think that would be Absurdism, but instead of reaching it, we can't understand it.