Welcome, bandyman and thanks for taking a moment or two to comment. I’m guessing you’re used to forums such as The Gear Page and other similar communities? 
Agreed. The appearance and organization of the forum leaves a lot to be desired. However, that probably has less to do with the migration and more with the choice of forum software. The old forum was xenForo-based (TGP, Les Paul, TDPRI and etc which seems to be the choice for many online communities) however, it was probably expensive to update and maintain. Singular Sound opted to use Discourse. In hindsight, they probably could have done a much better job setting up the framework for this forum—especially laying it out with an eye toward the future products they intended to release.
On top of the software engine, there are no guidelines that dictate any format on how users are to organize and post resources and even if there were, users would probably not follow them. 
The best thing I can offer is to choose how you want to see the forum when you’re online. You can set it up so your landing page is any of the categories or sub-categories. I keep it simple by bookmarking and using https://forum.singularsound.com/latest as I like to read all of the comments. If you’re looking for just the latest songs being posted, then you might prefer https://forum.singularsound.com/c/resources/song-files/24
There’s enough flexibility in Discourse so that once you become a little more comfortable with it’s idiosyncrasies, you’ll be able to quickly find what you’re looking for and especially once you get the hang of using the Search function. I like your suggestion to make better use of the tags. Search using Xmas and it illustrates what you’re proposing.
Maybe this hyperlink will help you: resources
Anyway, have fun on the forum and if there’s something you need help with but couldn’t find after searching, post your questions and somebody will chime in.