John Gruber has some strong B2B product management analysis in Was Salesforce’s Acquisition of Slack a Bust?
I think Slack is to Teams today where Mac OS was to Windows in the mid-1990s: better designed, for sure, but not in a way that makes a difference to the corporate IT decision makers who are making the call on which platform to use.
The key is not merely to be better, on some vectors. The key is to be better on the vectors that people with purchasing power care about. Missing this has been the death knell for many good products.
To use Jobs-to-be-Done language, there are strong forces at work when choosing a product. If the progress-making forces (“Slack is better designed!”) are not stronger than the progress-hindering forces (“Well we already use Microsoft, so we might as well stick with Teams”), people/companies simply won’t switch.