Well, if you don't like it that's one thing. You should play who you like first. But, let's take a character that's top tier and can just faceroll everybody. Whoever plays that character is going to be able to get away with lots of sloppy stuff and won't have to ever develop their game as much as somebody who has a character that has problems that the player himself needs to overcome to stand a chance.
The tier won't have a drastic effect usually but having a less capable character can force you to explore as many options as possible that you otherwise wouldn't need to. Even if the character is worse, your own skill as a player can be better.
But yeah what I'm getting at is, the important part is developing your skill, and which you can transfer between games and characters; at least, the basics of it. In games like BB you have to specialize in just one character if you want to go anywhere. They are too complex and different to just dabble in a few and get by.