If you look at the very right column of the three, where all the stories, are, then you'll notice that most of those (all but Light Big Groups, Bondage Big Groups and Extreme) are seperate into Humanoid and Exotic. The same applies to the Art and Literature section at the top of the middle column (again, except for Extreme). If you're looking for stories to read, just stick to the Humanoid section, avoiding the Exotic section, and you've avoided the centaurs and alien fish.
There might still be humanlike creatures, like elves, in the Humanoid stories, though.
In the one-on-one and player's wanted, it gets a little trickier. Some of the threads are tagged. If they have -E or Exotic in the tag, then again, stay clear of those. For the others, it's mostly a check and see.
If you're looking for games and creating a thread of your own, feel free to include that you're looking for a game with humans only, if you think the setting leaves any doubt about it. If you're setting up with someone, or if something looks interesting, don't hesitate to ask if it will be humans only. If it's not, then nobody won't hold it against you if you decide not to play after voicing your concerns.
That there are tons of games with exotic creatures, doesn't mean you must follow suit on it. There's plenty of fully human games out there, and plenty of people willing to play a fully human game. Don't let the not so human games scare you off!