In every case I've seen, Slack slowly replaces persistent documentation. Every issue one runs into can be resolved with a quick @here to the proper channel, or a DM to the tamer of Eldritch horrors (every company has one). This reduces the incentive to eliminate footguns or properly document everything, because look at us being all collaborative and solving problems together!
The smell for this behavior is having to search Slack for that last time someone helped you solve your problem. Slack is a great way to spread information, but it's a terrible tool to organize and store information.