"A slack that doesn't suck" doesn't exist, and whoever thinks Anthropic of all people are going to build that has no idea how this is going to work.

Slack has massive lock in due to cross-organization connections. The only way you're going to get people off slack is to build a 10x better mode for collaboration than river of shit chat, and while such models probably exist, you also have to convince people that they are better.

I wish whomever tries this the best of luck.