Hi, I'm new here, but just wanted to share my own experiences. When I first had my labrador Cadbury I went through the same as you, initially it was with puppy classes - at one I actually got told to my face "Oh no, not another chocolate labrador", at the second one I was reduced to tears. I went to one agility club, but again it was ruled by collies and I was not getting the help I needed - plus some of the owners thought it was ok to let their dogs have a snap at mine.

Well, I hunted and hunted and then I found my current training club where I have now been coming up to 3yrs. It is wonderful, the trainer welcomes all dogs, she has high standards for her agility but everyone is helped to reach them and when you are good enough getting told you can join the display team is like magic. In my class we are all friends, everyone helps each other out, there is only 1 collie in my class, sometimes 2 and everyone else has a different breed. Even on the display team we only have 4 collies and the rest of the dogs range from tiny terrier mixed breeds to possibly a Leonberger next year.
At the end of the day you need to be happy where you go. I made the mistake of trying to stick with a club where I was unhappy and I achieved very little with Cadbury, nowadays I can't believe I put up with it as long as I did!
There will be another club out there that's better and suits you, sometimes it just takes a while to find it. Good luck.