Thomas Shey
Legend
I'm the same. Actually, I think I'm pretty good at writing good descriptions. But on the fly--nope.
That's part of it, but keeping track of the spatial relationships in my head is a complete nonstarter. Ask me three successive rounds how far away a given thing is and I'll probably give you three different answers. And we don't tend to do loosey-goosey systems; 13th Age which we're doing now, is far looser than 99% of what we do (and even with it who can see what matters, so...)