Something can have the appearance and feeling of being great, but to be truly great it must be understood.
Well, the thing has inherent greatness. However, to appear great to any given observer might require explanation.
That seems a reversal of your prior position.
I don't think something has to be understood to be great. There's an awful lot of theoretical physics that's turning out to provide us with greater understanding of the universe. That in of itself is great, but I personally have almost no understanding of it. I still appreciate the greatness though.