I think the final thing was on the daily challenges; I always tried to solve them before looking at the answers even If I don't know the "proper" math to do so. I had posted my (correct) solution that I got to by writing a program to work it out; and I got some replies saying I was an idiot for not doing in the proper (math) way.
Please do email me silas [at] brilliant.org, so I can figure out which failure mode you hit and evaluate if it has improved at all since you quit.
In addition, as others have noted, our courses have no community aspect to them at all.