Fragmentation is something of an issue. I don't know if a given person at work mostly uses one of two chat applications or if they'll actually respond to an email. Personally, there's email but people I know use one of four different chat/text apps (five if you distinguish iMessage). Yes, notifications make some of that moot but there's a lot of fragmentation and I minimize my use of notifications in general.
(At work, it's partly that we've been migrating to Slack and you have people who basically only pay attention to slack and others who don't really use it.)
I still tend to favor email for a lot of things but understand that's increasingly a minority opinion especially for things that aren't routine updates, promotions, announcements, etc.
(At work, it's partly that we've been migrating to Slack and you have people who basically only pay attention to slack and others who don't really use it.)