To be fair, I looked at the meta rankings and there are a LOT of pokemon on there I didn't expect. Quite a few I like personally. It's surprising what you can do with different Pokemon. I found Abomasnow on one of the tiers (OU or UU I forgot which) and it has seven weaknesses. But apparently it's useful if you know what you're doing.
BUT, the dragons are overpowered for people who aren't as interested in competative battling. When I did it years ago, I had a lot of time to build up the best of the best teams and the GBC battles were link-cable only. Which meant that, in my small-ass town, there was a very limited pool of fellow competitors. I knew the top three Pokemon and it was relatively easy to prepare. It's global now, and I assume much more hardcore as a result. I don't know if I could put in all the time EV training and IV breeding that most metagamers do. Ergo, while I am interested in competitive battles I do not know if I could actually do it anymore. So I mostly speak from the context of in-game.
The way the type is structured, they do edge out a lot of competitors. Their relative scarcity is the only thing keeping them from becoming a larger part of the metagame. And it forced the steel type to rise up, as well, further limiting what you can do. They're not limited; they're limiting, and that's part of why I don't like them. In-game they don't suit my purposes well and out-of-game they pretty much pick the tone of your party for you.