Who would be deciding what qualifies and testing to see who is qualified? It appears that such a system would be far more open to abuse than the current one where all (except for non-citizens and some criminals) are able to vote.
I think I made that pretty clear already. If you're voting for a candidate but don't know what they stand for your vote is discounted. If you've taken the time to go and vote but haven't taken the time to know at least the headline policies of your chosen candidate why should your vote count at all?
The idea is to weed out votes based on arbitrary issues (like the people who voted Obama because it was "about time we had a black President", or the people who don't want Hillary because of the - ahem - things she and Bill must have been doing), it would weed out the tribal voters who don't know one candidate from another but can see that one has an R by their name and the other has a D, and the like.
I guess in a system where over 100% of registered voters can vote and it isn't deemed worthy of consideration, non-citizens can vote and apparently dead people can vote as well, there are probably bigger fish to fry than this. Sometimes it seems like we should have electoral observers from some other nation that's better at it than over here. Somewhere like, oh, maybe Iraq.