The others, like Garchomp, Charizard, etc. I can understand your point, though.
...Huh?
I've seen those guys used in wi-fi battles from people like shofu to great success.
Really, a
majority of mega evolutions are actually pretty good...but the real problem comes in only having one. Usually if you go competitive, you play to win, meaning if you come into a sitiution when you must chose one pokemon over another, you have to choose the best one.
A good example is Mega Gardevoir. Mega Gardevoir is really good and can get a powerful fairy hyper voice...but why use it over mega kangaskhan?
With that said Mega evolution is not a bad concept and was not executed poorly. All it needs it time to grow and for Game Freak to decide their next move on it.
Man, every time I see someone mention how Pokemon is unbalanced I struggle to understand the complaint when they are playing a game that is made to be unbalanced on purpose.
You're half correct. Yes, it has a tier system where you have to use pokemon of that tier is what is used, not all pokemon can be "OU," but you learn to get use to it and just use the pokemon in those tiers that you like.
If, by any chance you mean, "Game freak doesn't care if they make the game fun or not competitively."
Then you're wrong.
With no more permanent weather, a nerf to stealth rocks with defog, and fairy types, gamefreak is at least trying to make the game more welcoming to competetive players. That is, of course, if that is what you meant instead.