Why can't you have threads in a chat app?

This article is really, "We couldn't adapt our processes to Slack, so we blamed the tool and replaced a chat app with processes, because we're special snowflakes and how could anything Not Invented Here apply to our totally unique problems of communication?"

Sure, they ended up with a series of other tools to cover their workflows, the thing they "invented" was how those tools work together to cover the gaps created by not actually having a comprehensive and well-configured chat app.