I do agree that email quickly becomes messy, even with mailing lists. It's really much the same issue Slack has, a lack of training. It's just assumed that people will know how to use both email and Slack, but we don't. For email it's a decade old debate, that rational minds lost as Outlook dictated top-reply, forcing you to read threads backwards and discouraging the recipient from inline replies and cutting out irrelevant parts.
Slack is equally terrible, because the interface and threads is actually hard to navigate and I honestly cannot make search work in a rational manor. The more discusions you have in Slack, the worse it becomes.
Slack is the equivalent of shouting across the room. I copied anything that seems important to my notes. Any message that’s more than an handful of screen old can be considered lost.
IMO, that's a benefit of slack. At $LAST_JOB, we had a 30 day expiry on data in slack, which everyone was in uproar over initially. But, it forced us to actually put stuff elsewhere.
I thought so when I started at a company that had that policy but in the end we still mostly ended up with split-brain issues (eg some information is shared in both places, some in only one, some updates get lost) with the added negative that stuff disappeared from Slack.
It's just a hard problem overall when you have email, chat, wiki, docs, and a ticketing system.
And, unfortunately, all these things exist because not one of them is actually good beyond its scope (if it's even good within its scope to begin with).