If you can’t retrieve the knowledge easily it doesn’t exist. Basically impossible to find anything in slack older than a week.

I find search to be pretty good, regularly use it to find stuff posted years ago in a Slack community with ~27k members.

pretty crazy, given what it stands for: "Searchable Log of All Conversation and Knowledge"

But that's chaotic chat messages, you should really have proper docs in place and standard operating procedures etc.

Yeah I have never experienced Slack so maybe it works, but it's just hard for me to imagine relying on chat history (or, even email) as a source of institutional knowledge.

I don't have problem with slack history. It works.