So what's the end game there - using voicemail as a poor man's texting?
At that point one of two things happen. One is that telco's fix their networks. The second thing is they decide it isn't worth the effort, and let the traditional phone system die. Given phone calls are effectively free so there is stuff all revenue in them, I bet it's the latter.
If that happens it will be painful. Like it is with messaging now, but even more so. Messaging now is either SMS with it's limitations (like you can't use it from a computer), or a choice of a zillion walled gardens - Apple, Hangouts, Slack, Signal, Viber, Telegram, WhatsApp, Facebook, ... most of which I don't have installed so I can't communicate with someone using them. The voice equivalents are Facetime, Duo, Viber, Signal - many of the same things in fact. The result will worse than messaging - the ability to communicate universally with anyone dies, but with no SMS fallback.
But that's not the end point. Universal communication is just too useful to be dispensed with - as the explosion of internet and the postal system before that have shown. So something will replace it, and once again we will all be able communicate with anyone we please.
However, the replacement has to solve the parasite problem. Once the cost of sending a message drops below a certain point every universal system we've had so far has been overrun with parasites, aka spammers. The postal system has junk mail, email has it's spam, now the phone system, and of course SMS.
A solution may be to allow the recipient to charge the sender any amount they like for successful delivery of a message. Most people would allow friends to send for free, messages from unknown recipients to cost something, messages from spammers cost more.
That could happen with the existing phone system of course, but I'd lay log odds the incumbents have too much in common with the dinosaurs for it to even cross their minds. Sadly that means we are in for a very painful transition period. In fact they are already losing customers as people stop using land lines in droves, so I'd say the writing is on the wall.
https://news.ycombinator.com/item?id=21494300
[S]ince mid-2015, a consortium of engineers from phone carriers and others in the telecom industry have worked on a way to [stop call-spoofing], worried that spam phone calls could eventually endanger the whole system. “We’re getting to the point where nobody trusts the phone network,” says Jim McEachern, principal technologist at the Alliance for Telecommunications Industry Solutions (ATIS.) “When they stop trusting the phone network, they stop using it.”
https://nymag.com/intelligencer/2018/05/how-to-stop-spam-rob...
At the point at which individuals and businesses in sufficient numbers find the downsides of participating in the PSTN exceed the benefits, they'll start defecting to other systems. Likely small and closed networks initially.
It took decades for the telephone to become established as the principle means of business communication, and as it was, numerous other alternatives existed in parallel: postal mail, telegraph, telex (for what we'd now call b2b communications), fax, and early email systems.
Email seems to be dying along with telephony, and for much the same reasons.
It's occurred to me that much the value in social networks is in trying to corner a sufficiently large directory (that is, user base) to be able to credibly take on telephony. What seems to happen is that as these networks grow in size, they too fall prey to the hygiene factors already affecting telephone and email comms: spam and annoyance messages, with concommitant trust issues in the network as a whole.
Whether a technical solution to the trust and identity problem can emerge (and preserve privacy and protect against the surveillance state, surveillance capitalism, and surveillance by other actors (organised crime, racist or facist oppressors, stalkers, etc), remains to be seen. I'm starting to think that's a hard, possibly an impossible, problem. An essay of Herbert Simon's I've recently turned up is exceptionally discouraging owing to a critical error Simon made in it (claiming Nazi Germany committed it atrocities without the benefit of mechanical data processing -- it in fact had ample assistance willingly provided by IBM).
More generally, I'm suspecting that progress in information technology and communications capabilities reduce trust relationships, with some fairly strong historical evidence.
(Overall risks may be reduced, but the mechanisms by which this occurs replaces actual trust with validation, verification, and surveillance mechanisms).