There are plenty of working open standards to do the basics, its if you want to do anything beyond the basics that you end up in a walled garden.
Sure, you can still SMS worldwide, as long as they have a cell phone. But non-phone devices are becoming very common. What if you want to send or receive messages on your tablet or computer. (This works OK in the Apple world, but only because they hack it by routing SMS through your phone.)
Video calls don't even have that.
E-mail, for example, was different. I started using online services when you had AOL, CompuServe, Prodigy, etc. all in their own little worlds. That didn't last very long before they all bridged their internal e-mail systems to the internet and everyone could talk to each other.
Actually, not necessarily. At least with my provider (AT&T), I can set up my Mac as a validated device for WiFi calling, so I can do SMS and actual phone calls without using the iPhone as a relay.
It is a miracle that the web itself has survived as one of the few open interoperable protocols. Though I think this golden period will soon end, strangled by the death of net neutrality on one side and proprietary walled gardens on the other.
Ultimately, a commons is not compatible with unrestricted capitalism.
Sadly but somewhat hilariously, the thing which might prevent them a bit from offering exclusive-to-their-network content is the fact that in the US, you often don't have a choice of which ISP to go with, so if I really wanted some content which was exclusive to ATT's network, I simply can't switch off of Comcast (apartment building with no other option, past 3 apartment buildings were the same) since they've so successfully monopolized markets.
Edit: on the beginning: http://www.internethistorypodcast.com/2014/04/chapter-3-part...
I had hope for Hangouts, but Google dropped the ball big time in terms of user complexity and quality of product as they are wont to do.
I agree that video conferencing is rather fragmented but I'm honestly not sure how much that has slowed adoption. People just don't want to use video in a lot of cases. Essentially all my internal calls are on a videoconferencing system and I doubt I turn on the webcam 25% of the time. (We do use screen sharing a fair bit though.)
It is conspicuously absent on any other platform; even Android tablets can't use Duo, let alone a Linux, Windows, or macOS machine. So it's a hell of a walled garden.
Sure, bringing everybody together would be tough. You'd need a lot of discussion and probably glue/bridging code between different services. But it could be done! None of the big services are even trying to integrate with each other.