If you're serious about opening up literally everything and probably destroying all the leverage for possible business models how do you expect companies to keep providing the services you enjoy at the moment?
The Apple model where you buy expensive hardware and get exclusive software in the package?
The Microsoft model where you buy software and are still treated like a freeloading advertisement consumer?
Or the Google/Facebook model where you're not paying anything and the companies try to digest your entire life for the support of marketing departments?
You're describing the ones that smell like rent-seeking extortion.
How about the Signal model, where you get a free messaging app with published source code that runs on multiple platforms without trying to lock you into any of them, and its modest operating expenses are paid from donations to a nonprofit?
Or the Linux model, where a minority of users with the resources or technical capacity to make improvements are given the opportunity to do so, resulting in free software that anyone else can use too, and anyone could fork if the existing maintainers became abusive?
Or the Substack model, where you pay money for a service with no ads on it?
Huge dominant conglomerates being abusive is not unexpected. But why do we need huge dominant conglomerates? Let them cease to be.
There's nothing preventing Apple from requiring some kind of subscription for people to use its iMessage servers even if they were to open the protocol. All we're asking is for them to treat their service similar to premium email (which is also not free, but it's not all locked up either).
That's the extortion. Create a service with a network effect, so you don't have a choice in what to use because it's what your group uses, then tie it to another product and thwart anyone who tries to make a compatible implementation for any other device.
A more accurate way to phrase it is that Apple does charge for iMessage, but the cost is bundled into the price of your Apple device, and there's no way unbundle.
