The problem with your solution is that implementing it, while improving the quality of the platform as a whole, would not be in the best interests of the developers. Simply put, people are only using Steemit to make money. Nobody is saying "Wow, look at the quality of content on Steemit!" The ONLY draw to the platform is the profit possibilities. By fragmenting voting into niches, there will no longer be posts earning tens of thousands of dollars.
My proposal would perhaps turn 1000 Steem posts into perhaps 100 Steem posts, but likely Steem would thus be 10X higher in price because of the greater participation and utility. So nothing lost and only gained.