Along with this, can you also consider making smaller re-usable, stand alone modules.. (micro modules or features or package or whatever we want to name it).

For example - The category could be a stand alone module by itself. This has the main benefits

1. Multiple categories for a content : I can create a category called CATEGORY1 consisting of (News, Analysis, ...) and aother CATEGORY2 comprising of (Arts, Technology, Environment ... ).. Now in the posts form I can have two different "relationship" fields pointing to the categories. One field linking to CATEGORY1 and another field to CATEGORY2. So one post can be a "News" related to "Environment". another could be "Analysis" related to "Environment".
2. Re-use Categories across different modules : Currently the categories under Posts are different from categories under other modules. So I can't list all the "Environment" related content since Videos and Posts have different "Environment".

You can continue to package "posts" as it is done currently (with the sensible defaults having one Category field). But advanced users will have more power.

(There is a thread related to taxonomy here - https://unacms.com/d/building-a-dedicated-taxonomy-module-for-una, but I added more details here thinking the relationship could be re-used.

Also labels cannot be an alternative. It could be a short term workaround though. Categories are for Site admins / operator to structure the site. Labels are for users to dynamically organize content.