Feature demo of a modern replacement for email

I watched the demo and it has some neat features, but email is not broken for me. Email still works great. Can someone explain their pain points with email so I can understand why people are putting a lot of effort into reimagining it?

EDIT: I should clarify, most of my “pain points” with email are things that can be solved with a different email client. I like features such as “remind me to follow up in X days”, “archive all replies to this thread immediately”, support markdown, etc