"Instant messaging" is just as disruptive as email if you have notifications turned on. There is zero difference between your email program going ding ding ding on every incoming email vs slack/teams/whatever doing the same.

My current company has _all_ of their communication on Slack, the only emails I get are meeting invitations and status emails from automated systems that haven't been integrated to Slack yet.

I can easily click to pause notifications on Slack if I don't want to get interrupted - or I can just close it and read the backlog when I have time to focus on it.