Ask HN: Never held a job. In what ways companies use email internally nowadays?

High schooler here, looking to make something involving email, for teams. I want to attempt to bring email to the 21st century, so to say.

With Microsoft Teams, Google Suite and all the other collaboration products around, how is email still used? my impression of email is that it's very hard to use for communication because it's too formal, so it's hard for average people to communicate with (it's harder to write a single, well-read, overelaborate email with all the details, than it is to send instant messages back-and-forth asking and answering questions.). So I think companies use email mostly for external communication, but internally they only use it for matters of significant importance, akin to notifications. But even that can be done with Slack channels. So is email useless for internal use?