>I think its demise is closer now than at any point in the past.
Quite the opposite here (we're b2b in Europe), most of business communication is via email. It's the easiest way to contact a business because virtually everyone uses it, as opposed to the hugely fragmented market of Telegram/Whatsapp/Discord/Slack/Messenger/whatever is the new shiny thing this week.
Our SaaS is about eLearning, we have thousands of clients in US, Europe and Asia, from all sorts of industries. A company usually registers all their employees in our system, and every employee has a profile where they can specify their email (which is optional). I worked with tech support and although I don't have exact statistics, my impression was that the majority of employees have emails assigned, it was the norm, rather than an exception. I've noticed it's usually retail where employees only have a phone number.
We do use Telegram/Whatsapp for announcements, but I don't see email go away any time soon. I can't imagine myself having an official business correspondence on Discord.