Group chat as the main method of communication leads to:

• Mental fatigue and exhaustion. Group chat feels like an all-day meeting with no agenda.
• An ASAP culture. Everything must happen now! 
• Fear of missing out or not having a say. If you don't pay attention all the time, you might lose out.
• Thinking a line at a time instead of complete thoughts at a time. People can jump in before you can fully present yourself.
• Implied consensus because "we talked about it in the chat room."
• Knee-jerk responses. You only have a small window to make your point before the writing scrolls away.
• Lack of context.