Flarum is actually configurable, you can change the default landing page to be Tags, but the layout isn't the best.
Personally, I don't think Tags is a user-friendly concept. They are powerful, yes, but they are not user-friendly.
To me, a hierarchical organization makes sense for someone new to the community. It is a simple and intuitive concept. Fortunately, you can build such a concept using tags:
https://discuss.flarum.org/d/38778-friendsofflarum-categories
Personally, as someone who uses forums a lot, my default view is always going to be the Latest index. However, this is not a new concept by far.
Here's an example of a very old community on very old software that has a such a view:
https://forum.pianoworld.com/ubbthreads.php/activetopics/30/1.html
In fact, I think this view is quite superior in some ways, because all the latest content is immediately accessible and you barely ever have to click individual articles to read them. Contrast this to Flarum, where you only see the titles.