Like everything in life, it's always a trade off. You may gain scores for team work but will sacrifice individual creativity. Deep creative tasks always require a full strength of focus and that state is only attainable once we allow our mind some time to completely "dial in". You simply cannot switch from 0 to 100 and be in the zone within the span of just a few minutes.
When you are using Slack or any social media communication platforms, your brain must allocate cognitive resource to manage your ego because you do care about what other people think of your opinions. Since the pool of our cognitive resource is limited, we will have less remaining that can be dedicated to other real creative tasks.
On top of that, you now have a distraction source where you constantly have to switch attention to. This may condition your brain over time and cause it to lose the ability to "dial in".
Some companies were eager to force employees into using these tools while it didn't really provide any real tangible benefits, and may in fact even be destructive. Within a company only some departments should use it but some definitely shouldn't. It's the same reason why open office concept may work for certain organizations but not for all.