You have to go deep down usage charts to find stuff that's not viable in some way or another. Currently Pikalytics goes 86 pokemon deep before you can find something below 1% usage, and there's stuff that I've seen put to good effect even below that. And then within that wide spread of viable pokemon is a lot of diversity in movesets, items, abilities, and stat spreads.
It's part of what makes the game so difficult and interesting; there's so much potential for what any given team could be aiming to achieve, and you only have a little bit of time to process all the possibilities in your head. Specifically, 90 seconds in team preview, and 45 seconds per turn. That also creates this fun push and pull, where less standard pokemon can become innately more viable for the sheer fact that your opponent is less likely to be prepared for them.
It's great. I don't want to trash on Smogon metagames, because a lot of people really enjoy them, and that's perfectly fine and I'm happy for them, but I do want to stress how incredibly different of an experience VGC is from the ultimately very condensed and chesslike metagames that each Smogon tier eventually settles into. If you've ever been alienated by that, but still like the idea of Pokemon battling, definitely try doubles.