Atlassian products are more mission-critical. Most companies actually need some tool that does what Jira or Bitbucket does. They don't really need Slack.
People where I work would much rather give up Jira instead of slack.
Do you use Slack?
You don't think it's Mission Critical?
I've worked at companies both with and without Slack. Something like Slack might be mission critical for a remote-first company, but comparing the two situations, I've actually noticed better communication without Slack than with it.
We use slack at the three companies I currently work on and it's mostly a distraction and a place to quickly share files. It's good for some shared notifications. My most active slack is one I have with friends.