Majority of people cannot tolerate Tren but there are exceptions just like any drug. I can run 900mg of Tren with only one mickey mouse side effect. People don't recommend Tren or Tren Ace first because the "surprise" is too difficult for people to deal with.
Tren is also very misunderstood and is an amazing bulking compound to pair with proper diet and training. Problem is people have no idea how to bulk on Tren because they don't understand enough about nutrition, the compound, and their own body beforehand.