As the water descends the mountain it spreads. The current becomes gentler, the riverbed much wider. A great many plants and animals drink from it here, but the water is not as deep. Finally the water reaches the level plain where it spreads out very greatly. Here even the most delicate of wildflowers partakes of the moisture it provides.
Depth is almost imperceptible, but the life it gives is every bit as potent.
I think Torah is like that. The Tzaddikim are like the great trees, few and strong, and able to comprehend and absorb Torah at its deepest and most potent. It should not be our concern that we are not oak trees. Our job is to drink and bloom. I saw a rock blocking the flow of a stream I passed a short while later, and wondered the meaning.