I think it is mostly that people find discourse to busy looking. But I’m glad seeing this minimal discourse discussion etc.
You’ll have to be a lot more specific about what you want, if as stated in the above quote you want the homepage to be the categories page simply edit the topnav site setting to put categories first.
I mean simply let discourse look just like a phpbb forum with more functionality. But I will play around with some CSS and see what I can get.