Productivity, on the other hand, is through the roof.
My understanding of the parent post was poking fun at the fact that these chat spaces (Slack or otherwise) allegedly end up being a productivity loss as people spend more time finding the meme-of-the-week to post rather than working.
Nothing to do with the viability of Slack or whatever instant messenger you choose to use.
Maybe use this as an example that you guys shouldn't do that?
It definitely was a neat project using chat flows, but I ultimately said "this is great until slack is down". Slack promptly went down the following week and we just threw our hands up and used the AWS console.