The game is pretty unbalanced, and Black Canary is pretty bad because she has a hard time dealing with the zoning.
But with that said, zoning is intentionally built into the game, and a lot of the cast can combat it pretty effectively.
Personally the zoning in the game isn't for me, I don't enjoy that type of game. I enjoyed playing Robin but having to spend most of the match wading through projectiles (which do a pretty significant amount of chip damage), isn't my idea of fun.
However it's not broken. It's just not appealing design, for me. One of the things I really hate is seeing people die at tournaments to chip damage projectiles. It's just straight painful to watch and feels unfair. Often the last hit comes off of a knockdown, then they wake up only to get hit by a meaty projectile. It's a stupid sequence of events, and I would argue bad design - why let your opponent get up if they will only die? There's no gameplay value for either player in that experience.
You just described counter picking, not unbalanced gameplay.
I also stopped reading when you started complaining about players being cheap. Nothing is cheap. Learn to deal with it. If you can't deal with your main you might want to jump on that counter pick bandwagon... Either that or just keep complaining?
I think it's fair to say that the game has some pretty easy to play strategies that tend to result in success, and equally, it's fair to say that you don't like the gameplay design in certain areas. While it's perhaps unfair to call it cheap, the term ultimately often just expresses the players disatisfaction with the games design, an expression I think they're perfectly enttled to.
For me, I don't like Injustice's zoning. It's not that I need to 'learn to deal with it'. I don't enjoy the gameplay it creates. I don't like how one sided some of the fights can feel (counter picking is one argument, but it's also fair to say I enjoy fighters where each character feels more closely matched) and I don't enjoy having to play a guessing game against projectiles - because of how fast they tend to be, its often anticipation rather than reaction that's required, i.e., quite often, you're forced to make a guess (or hard read) if you want to get in and deal some damage.