Earlier quoted context omitted.
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.
My personal take is that, as long as profit remains a guiding priority for a society, there will always be much greater incentive to create a new and successful walled garden than to share and contribute to open standards. This is made evident by countless technology firms and other industries.
Slack and other tools are solving a problem customers have and they should be compensated for it, especially given much of their users are profit oriented enterprises.