Why does this forum hate everything, I wonder.
As repeated thousands of times before, tiers are based on useage, if Pokemon X raises in useage, it goes to OU, if it lowers, it goes to UU, if it lowers further, it goes to NU.
Nothing is stopping you from using the Pokemon you like. OU Pokemon are in there for a reason, people know they work, so they use them to win. If you like a UU/NU/BL Pokemon, good for you, if you can use that Pokemon in a higher tier efficiently, then that's great (Note the lack of sarcasm). If you can't use it efficiently, then throw it out and find something else. I went up 150 points on the Smogon Standard Ladder by using a gimmick Regigigas set. I like it, I used it efficiently, I won, end of story. On the other hand, I tried another Pokemon I liked, Mantine, and plummeted competitively. I liked it, I couldn't use it efficiently, I threw it out and added Regigigas.
Winning is all that matters in competitive battling. You play to win, not for fun. If you can find a way to combine winning and fun, awesome, because you're more likely to win if you're doing something you enjoy.
In fact, you don't even have to abide by the tiers, go off and make your own Shoddy Server, make your own tiers, hell, even add some Pokemon.
In short, shut up, ignore it, and go do something else.
Wee, first non Garchomp related rant.