It constantly drops notifications. It spies on people, showing you when they are logged-in, even if they just want to quietly read. Logging in takes about 45 seconds on my slow computer, and inviting people is a PITA, and you have to pay them or they delete everything after 30 days or whatnot.
Discussion
Also scans all chat channels for AI training...by default. This can only be turned off by emailing Slack customer service. Even then you are tursting that they actually stop.
Slack is a gigantic feature set to replicate. Anyone who does it on Nostr should come up with a funding model.
Maybe private groups get a hosted private relay, and groups can pay for that hosting service.
Otherwise groups use shared relays, and there's no guarantee of privacy unless all messages are encrypted like DMs.
Slack was a mistake and should not be replicated. We need nostr irc. It's perfect because there both have relay right in the name.