Oh, fairy types could definitely have been done so much better.
I agree with you that while Posion and Steel have few type-advantages, they're meant to be defensive. Plus, Steel gained an advantage at the cost of it's ghost and dark resistances. Bye bye, Metagross and Bronzong...
Although at this point, we all know that Fairy was just introduced because they wanted to nerf dragons, ad instead of releasing better ice types they introduced a whole new type altogether.
And that's my main problem with Fairies. They were released for that reason alone, and it came at the cost of rather nonsensical Weakness/Resistance/Advantages.
I supported Fairy types because I like the idea of changing things up drastically by adding a new type, but it was SO poorly done.
That being said, we don't need any more new types at all, so I hope Gen. 7 leaves that alone, as well as gives us a much bigger list of newly introduced Pokemon, maybe more electric types, we don't have enough good ones in recent years.