I 100% disagree. I love threads in Slack. In fact, we actively encourage their use in our workplace. Not everyone in every channel needs to be involved in every discussion. If someone on my dev team says, "Hey, I'm having a problem with X", one person can respond in a thread and they can have a little discussion that doesn't ping everyone else all the time. However, other people have the option of contributing to the discussion if they wish. In addition, the thread can be found in a search at a later date if someone is having a similar problem.