I challenge you to do it better. Ah, screw that. I don't think you can, the way you talk. I challenge you to do something much simper: Read an RFC and try to provide interview style non-compiling code to implement it, then write a single blog post explaining what you did, applying a correct and reasonable free license to your source code and your blog post. That's something an untalented hobby programmer can do if he puts his mind to it.
Still, he is stil "working on it". While Slack has already "delivered".
It is childish to say that whatever feature Slack has is "simply" something that can "just" be added to XMPP.
To me, the author's complaint of how Slack rips users of is the same as customer who complains when it takes month to "just" add a feature.
He himself hasn't even done it. He planned to do it, anybody can plan to do things. Anyone can be working on something that will change the world. Only few delivers. He complain about funding, while he is adding feature that he claimed was "simple".
Why does simple feature needs funding? And if Slack is ripping people of on feature that can simply be added on XMPP, then put your house on loan, create better XMPP client and earns millions of dollars. You don't need funding. That's what being adult is.
This is not what the article says. The article says clearly that everyone knows we want these fancy UIs in open chat apps. But the problem is funding. You need to pay 10+ developers, each costing between $100k and $200k (50-100 without tax) for 1-3 years to get such a nifty UI and after that you still need 1-3 devs each year to keep up with all the changes in the IT world. Someone needs to PAY that to get such a nifty UI.
The article also argues correctly that you are currently paying for it by giving away your data which is worth a lot more than a few 100k USD/year. And all you get is a more nifty UI. Wow.
And instead of understanding that you are exploited you complain about how stupid the people are that fight for protection of your values. That is REALLY stupid. The same level a child complaining about needing to go to bed early than the parents while the loud and colorful ads try to keep the child in front of the TV until 2 am or longer.
Start acting like a grown up.