This is what I see as well.

"I ran into X, tried Y and Z, then asked Bob, Bob wasn't sure, anybody else have ideas?"

Or

"We discovered a dependency on Team Z to complete Q, Mr Bossman, can you talk to their manager, as the engineers weren't sure what to do?"

And yes, both of those could be handled in Slack. But, as a manager at a medium/large company, the amount of Slack messages I get daily is MASSIVE (both direct and in channels), so a face-to-face has some value in getting the issue front-and-center (and not lost in a pile of clutter).

Yes, in a perfect world, there isn't all the clutter in Slack. But, in 25 years in industry, that's rarely true.

slack is a slug

we need to reduce the number of slack messages. not increase the number of meetings.

i want to build something like that at some point.