For me it's just all the funny words for highly specific descriptors of particular types of terrain. But also, you can somehow still get such a vivid picture and follow the gist, even as you filter through all that, even if you don't bother to look it up.

"Along the left was an eylet flanked by a hithertop which flattened as they proceeded north through the shallow wolly, which rose into semi-steep clifftons..."

(Yes I made all that up lol)

Somehow even with my ADHD I'm having such a good time with it...because it's so vivid, like Tolkien was actually there.