Skype for Business has been replaced by teams which is not much better and pretty much still an awful chat application.

Teams is worse in that it appears to actually be Electron instead of the semi-native (I don't think it's pure Win32, judging by the UI latency and appearance) Skype for Business.

Being awful is Skype's killer feature. You can't carpet-bomb with pings, you can't comfortably copy and paste code or logs into it, half of devs who use linux don't bother running it on a VM and instead use flaky third-party clients, it eats messages randomly, so long story short - people generally avoid it except for trivial shit. And on the odd day when they don't, I get a copy on Outlook anyway.

I've read some horror stories about Slack, and I shudder to think what would happen if my company moved to it.

only for the cloud version.

S4B server edition is still in active dev