The internet was built on open standards.Potentially, but the legislation might be the very big stick that will get these discussions going and trigger the detailed work necessary to make it happen.
We already had messenger services that were interoperable. They weren't all encrypted and far from ideal, but they existed. Rather than expanding on them, we seem to have gone in the complete opposite direction.
I think we can disagree on whether or not government intervention in this space is a good idea or whether the ends are justified, but I think it is likely that all the work you mention will not happen in the current market unless companies are being forced to play nice with each other.
Tech companies closing their standards goes against that idea.
If it takes legislation to wake them up then so be it.
There is a reason the internet was better 20 years ago.