User blog comment:BIA-Kaboose/The Problem Behind Balance/@comment-5883057-20131211130411/@comment-8267817-20131212135707

It isn't that Riot is doing a particularly "bad" job at balancing, it is that they could do better in situations, allowing all champions to be at least somewhat viable, too many champions don't get played because most players feel that they are weak, and most of these champions are older ones, because at the time they were popular they were problematic, as newer champions came out they were forgotten, traded out for champions that did roughly the same thing, but better.

Some champions have really fun and enjoyable kits, but they are simply unviable when compared to what they might end up facing.