Edit: I should have pointed out that the article doesn't say they don't encrypt the data, it just says they don't end-to-end encrypt it, which by definition would require it to be impossible for Slack or anyone else to read the messages (other than the users who sent them or were in the channel at the time they were sent). Only a handful or recent apps like Signal and Telegram even
attempt to do this.
Any form of communication (or really any form of information storage) could be sensitive, that's my point exactly. There's literally no reason to mention Slack other than it's hot and the author could glom onto a trendy brand name to get people to read an article that is basically devoid of any novel content.
If a new sport which merges football, basketball, and chess become popular, we would see a bunch of articles 'People Who Play Chessketball are Getting Injured'. 'Chessketball has an Injury Problem'. 'Things you Need to Know before you Let Your Children Play Chessketball' Yes, people are more likely to be injured whenever they participate in any physical activity. Also when they ride a bike or go for a jog. Also, it turns out, if they don't do any physical activity at all they will suffer from heart disease.