Steemit already has subcategories which act as a filter; for example, "homesteading"..
Adding more specific subjects might help, but in the end there's going to be a flood of screed on Steemit ... It just goes with the territory ....
So I disagree with you because growth trumps your complaint ... And your complaint can be fixed without sacrificing massive growth...
Finally, in this globalised world if your brand isn't growing it's dying. Think about that. I understand quality content is important, but most people aren't writers and they never will be so get used to it....
Filtering the content should be automatic. With current tags there aren't anything automated, users have to make an effort to find and see everything that is posted with a certain tag. Users can't even subscribe to a tag.
On the contrary, I think it will be absolutely necessary to fix the UI/UX if we want to have millions of users. With the current UI the experience will be so bad that the system will become unusable and old users will leave and new users won't join.
"Filtering should be automatic "
Yes, that's what I mean. Fix that. Problem solved... Growth continues...