At one point in time I also tried a variety of classes and clubs: orchids, native plants, environmental, dance, acting, the list goes on and on. I failed to make a single friend in that manner. In my personal opinion, based solely on my own experience, NTs usually are not looking to make new connections. Their lives are already full, they have their friends, and their time is filled up with their current friends and whether they find you interesting or not, they just don't need a friend.
Fifasy, I find you interesting and I see sparks of personality even in your posts, so I don't think that being boring is your problem. If I really want to participate in a class or group like you describe, I try to thing up ahead of time some bits that I can contribute. For art, instead of saying "that's a nice picture," you can develop your own list of art comments, such as "I like the use of color here," or "perspective" or "what are you trying to say with xyz." And then, as another poster stated, listen. Usually people like to be listened to.
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The river is the melody
And sky is the refrain - Gordon Lightfoot