FWIW, they added the ability for these companies to control their own integrations by publishing iOS and Mac apps.
It's just that so far, only Twitter has bothered to do so on Mac. Even software like Slack which does so for iOS just hasn't bothered to port that code to their Mac app - most likely because of the Mac app using a different Electron-based codebase.
I'm about this close to making an e-petition demanding Snow Leopard FOSS for posterity, now that they have successfully milked us all multiple times.
My 2011 hardware works just fine, and 'obsolete' is meaningless in a world where IRC was replaced by Slack and where Visual Basic tutorial fodder from 1998 become MVP web products...
It is extremely frustrating. Especially when Catalina removes features that were working perfectly.