My personal opinion here. We (NodeBB) decided to go with categories from the get go because it was a form of hierarchy that worked well for YEARS, and you don't go breaking things that work fine.
IIRC Discourse started without categories. The whole "bucket of messages" shebang. It did not go well, in the sense that I believe people kept asking for categories.
There's something special about a curated list of folders to slot messages into, that tags and labels don't quite capture.
Currently, the user is being presented with most things, so I think my framing matches the actual user perspective with better accuracy than a cheerier wording. ;)
IIRC Discourse started without categories. The whole "bucket of messages" shebang. It did not go well, in the sense that I believe people kept asking for categories.
There's something special about a curated list of folders to slot messages into, that tags and labels don't quite capture.