You're right -- a lot of people who yearn for the spatial Finder don't remember how many fewer files/folders we had in the past, with a lot less hierarchy.

But for those who loved the spatial Finder and did indeed have nontrivial numbers of files, well, some people just have exceptional visual memory. Think of those who have thousands of books in their house with seemingly loose-to-no organization, yet can quickly retrieve any volume. Or cooks with pantries that seem to lack any rhyme or reason, yet they can immediately find any ingredient.

The one person I know who loved the classic Mac OS spatial Finder and dealt with nontrivial numbers of files worked exactly like that. Their files were organized in haphazard piles across an incredibly cluttered desktop and a handful of folders, yet they could always track down what they needed. Their brain was essentially a flat key->value store that mapped files -> screen coordinates. It didn't map files -> filenames (lots of "memo_1.doc"), and it certainly had no notion of hierarchical keys.