Signal's product focus has been at best un-encouraging to those who want to use it for anything else. Federation, I'm looking at you, but you've also got to take it in the sense that every single vendor that embraced the only realistic messaging federation standard of the 21st century went on to embrace and extinguish it in less than a decade.
This speaks to a few problems: 1. Messaging is hard 2. Security is hard 3. Logic about security is hard to reason. 4. Historically, anyone paid enough to care about this space hasn't had any sort of public interest at heart.
Any application that combines any of the three falls squarely into what the people at Latacora and the like would call a high risk application. I might disagree with much of their analysis, but in the lens of risk control, they are perfectly correct.
If you're trying to figure out how we got here, you've also got to realize that there was an avalanche of government and commercial entities whose goals are not in alignment with say, those who think the optimal solution is a home rolled provable trustless security system.
For myself and many engineers I'd bet, I'd say that's where we thought things should go in the 90s and early aughts. Some things are better now, but most are much worse.
Society and encryption's implications I would say have caught up with each other, and theres definitely something found wanting. There's definitely say a market opportunity there, but there's also another big challenge that I read reviewing a discussion about package signing lately: "Nobody in this space gets paid enough to care."
That's what separates people like Signal, even if some of the engineering crowd doesn't like the way they delivered.
This is a bit of a ramble, so there's two afterwords:
1. Much of the morass about PGP is explicitly due to the environment, space, and time in which it was developed. This does not boil down merely to 'it wasn't known how to do it better.' There were decisions and compromises made. I think the writer at Latacora is not giving the history of the piece justice. That's OK though, because that's not the crux of their argument. It would be good though I think if they gave that a further explanation than why things like the byzantine packet format are impossible to explain, even if that explanation were only a footnote and reference. (Writing the history of how it got there is absolutely doable, but it would make for a dryly humorous history, at best.)
2: The open source and (linux/others?) distro community has tried hard, more than once to make this work. The development, design, and implementation burden though, is gargantuan. The overarching goal was basically to be compatible with every commercial system and maybe do one or two things better. What the article casts as purely a liability was the only way to get practical encryption over the internet well into the early '00s.'
Regardless of all that though, PGP is still a technical nightmare. If you dismiss it though, even when we have better components, I worry that we'd only repeat these mistakes. If you work in any sort of crypto/encryption dependent enterprise, please find and study the history. Don't just take the (well considered) indictment of PGP at face value. There's important lessons to be learned there.