Go ahead and make your own decentralized forum, there is nothing preventing you to do that, and see how it goes for you.
You cant just expect that magical decentralization would fix all the problem in the world like censorship, it is childish to think like that.
I am not even sure most of the people would enjoy non-censored bitcointalk forum, and they wouldn't like to live in world without any censorship, it's just a pipe dream.