Discourse allows for more clear organization of sub-categories.
To enable this, these two settings need to be enabled:
The first ensures that subcategory topics do not populate the parent category, which keeps the conversations cleanly in different section.
The second shows the subcategory sections as boxes, so that users can easily navigate to the subcategory, and see the latest posts in that category.
I think these two settings would be good to have on each parent category.