Earlier quoted context omitted.
Rather than open or closed source programs, let's have interoperability. Then everyone can choose. I believe Facebook was aiming for something like that with Threads, and was playing to have WhatsApp and Facebook Messenger be open to a specific standard as well? I fondly remember the days of Pidgin and Adium..
Proprietary services are interoperable in the beginning and then stop. Both facebook and google supported XMPP but that's no longer the case. Slack supported XMPP and IRC, but that's no longer the case. It's completely pointless to expect proprietary stuff to be interoperable. It requires constant reverse engineering and remember that they have money to throw away to hire developers to make breaking changes to the pr…
XMPP isn't dead either. Here's an open source project of an XMPP based Slack - https://prose.org/ (I have no association to this, was amazed how much digging it took me looking for Slack/Discord alternatives to find it.)
The most damage to open communications software probably came from the closed mobile app stores. The barrier to maintaining a working app simultaneously on iOS and Android is high. Almost every iOS game I bought 10 years ago is inaccessible and no longer downloadable. Those barriers are in the process of being torn down too, with or without AI's help.