I don’t know if I have a solution, but I have some thoughts about what kind of solution would work, which might or might not be helpful. I think they’re mostly implicit in what folks are suggesting, but it’s helpful to me to state it explicitly:

1. A solution should be intuitive for new users.
I’m a fairly new user, and am myself no doubt guilty of some accidental tag abuse, even as someone who’s trying to learn the community and be at pains to educate myself about Steemit best practices. I’ve been tagging posts like I would on most blogging websites—make sure you fill your five—even if some of them are less focused.

A solution should be something new users gravitate to on their own.

In other words, some degree of psychological nudge-design may be in order.

2. It should be non-coercive and non-punitive.
A decentralized system with a broad appeal doesn’t seem likely to grow and improve through more policing. Again, a path-of-least-resistance solution makes the most sense. Eventually, the police won’t be able to keep up, and without a central authority backing them, the police become just another faction—and an ill-tempered one at that.

I also think in this particular case, a punitive solution risks alienating serious artists whose medium of choice is camera-phones, or people with good equipment just starting out who are bad, but well-intentioned photographers.

3. It shouldn’t require additional development.
This is maybe wishful thinking, but again, it seems like a solution should emerge from the community. It strikes me as contrary to the ethos of blockchain to appeal to a central authority to solve the community’s problems. Even though some of my favorite solutions from the replies involve changes to the UI/structure of the site. Personally, I think the simplest development-based solution would be to restrict the number of tags per post. It doesn’t eliminate the problem, and it’s a little coercive, but it obliges users to make decisions and clarify the purpose of the post. Obviously, current users could do a version of this by choosing to restrict ourselves to two or three posts, and concentrating upvotes on posts with fewer, more concise tagging.

4. It should be able to handle some level of intentional/unintentional abuse.
This combines some of the points made above, but basically, people are going to try to abuse it, or abuse it by accident. It needs to be able to survive that behavior.

So, in light of my idealistic list of requirements...I like the idea of voluntarily limiting ourselves to fewer tags per post, and concentrating upvotes on posts with fewer tags. Obviously, there are issues with that, but it rewards purposeful posts without punishing others. Still pretty subject to abuse, I guess.

I also like the ideas that involve new, more specific tags. I just think that energy would need to be put into making those tags attractive to users.

Sorry for the giant post. Hope it’s at least a little helpful.