There's no need to rake. The leaves are the natural mulch those trees are evolved for. Raking removes the organic matter which would otherwise be returned to the soil.

Native ephemerals like Erythroniums evolved with deciduous trees and make use of the light before he canopy closes. You could explore those.

I haven't been raking so far, unless to add leaves from beyond the trees themselves. But I have wondered if this precludes me from growing anything there. It's just so deep.

I'm curious as to why it's so deep. What can be stopping the leaves from rotting down naturally?

The trees are very large so they drop a lot of leaves. I also think surrounding trees contribute.

Daffodils, Lycoris, possibly ferns.