My point isn't that cloning is easy. More that it has already been done multiple times and Slack has very little lock-in. And enterprise software has less network effect. Our IT department could dictate use of Microsoft Teams next month and it would probably be fine.
It had been 'done' by IRC 20 years ago, Google had already been heavily in the space with their linking to Gmail and Hangouts and previous attempts with things like Wave.
Yet somehow Slack has come in and taken a massive share of the market in a matter of 5 years.
