Thanks for your great feedback. Atm dMania is still tied to Steemit and most users want the visibility and upvotes from Steemit. That's why users can choose their own tags.
It probably won't stay like that. There are still some technical limitations why dMania can't have it's own tags. For example I can only query the most popular Steem tags. I probably would have to track dMania tags myself or create predefined tags.

For the moment I think dMania is fine like it is. 9GAG for example had millions of users before they added tag pages. I will work on it when there are more users and posts.