The fact that we still get surprised by new elements of the brain suggests that there quite a lot we still don't know about the brain
Indeed, and more big surprises are bound to surface.
and uploading might be harder than previously believed
I'm sure uploading will be hard, but the discovery you mention (which looks like some extra plumbing infrastructure for the wetware at this point) does not seem to fight the idea that the cognitive processes can be abstracted and extracted from the wetware.
Kipnis et al found a new part of the lymphatic system. It goes into the brain.
The fact that we still get surprised by new elements of the brain suggests that there quite a lot we still don't know about the brain and uploading might be harder than previously believed.
Given that these vessels were hard to find, it will be interesting to see whether other hard to find vessels will be discovered in the coming years.
Besides their Nature article Structural and functional features of central nervous system lymphatic vessels, there a good article on NeuroscientistNews titled Missing link found between brain, immune system -- with major disease implications.