I'm relatively bearish on Slack, but who knows what will happen in 5 years. Anecdotally I find a lot of people (myself included) have long shifted from "Slack is the greatest thing ever (e.g. 2015/2016)" to "Slack is more annoying than email." At the same time, I don't feel like there's been much new outside of changing the design of their homepage every 3-4 months (can someone explain why it makes sense to throw design/eng resources on this?) and search is still terrible.