Well deserved. Their product-vision was clear, their execution focused on what mattered... and they didn't need to bend or break laws to succeed. It's easily my favorite unicorn of the past decade.
You are not wrong :-). In fact, your second line is completely correct. However, Slack has lowered the standards for desktop software by being a really terrible piece of software. Which means that the professional in me wants to see a decent client before I'm happy. What's more worrying is that we are rapidly moving away from an Internet based on open standards and into walled gardens.
Other electron based apps like Discord perform better so I'm not sure why Slack is so crappy.