Re: No, consistency is a FEATURE.
new is always better
I was reminded of VAX Notes. It would be derided today for its glass teletype interface, but it was transformative - certainly internally in Digital - at the time.
I'm far too old to have any exposure to Slack, which might be why I'm suspicious of any solution, whoever the supplier might be, that depends on your critical business functions being performed using a proprietary solution hosted by a third party. A hosted open solution you can migrate elsewhere, yes; A hosted proprietary solution you can migrate in house, perhaps. Chucking your stuff into the cloud and hoping it will be there tomorrow. no.
And it really isn't as if there aren't alternatives.