A player would have to be very naive or self-delusional due to degeneracy to conclude that collusion isn't rampant at ACR.
1. The world is full of cheats. Poker players aren't known to be more ethical than any other group. Actually, the opposite is obviously true.
2. Colluding is very easy with all of the modern communication tools at our disposal.
3. Most importantly, WPN isn't attracting top talent in tech or security. This is obvious from the new version implementation, their rich history of server problems, and DDOS attacks crippling the site. It's impossible to have a logical belief that they are proficient in catching cheaters. They didn't even attempt to stop the bots for years until so much evidence came forth and people started making ample noise about it on youtube and the like.
4. I witnessed collusion without a doubt on one occasion and suspected it in other occasions. I reported the obvious collusion to the proper WPN authorities and it was completely disregarded.
Please understand that ring games exist before replying to this post about how it's difficult to collude in mtts.