Never mind that i fear that the black hats of the world will always find a way to break the sandbox of the "safe" computers, and thus we are effectively fucked. Because now they have access on a level the rest of us do not, and thus can't counter their actions.
BTW, i do believe Cory Doctorow has done a couple of speaking tours on this under the titles "The coming war on general purpose computing" and "The coming civil war on general purpose computing".
The first being about government demands for a computer that do everything but some naughty action, and the second about well meaning geeks locking down computers to make them "safer".
I think split world is livable if that divergence is embraced. Running a Xeon server as a workstation is something a lot of developers do. As clients get more locked down, it's probably the direction we'll have to go, and really differentiating what makes a "server" from a "client".
It's good you brought up cars, as they're a perfect example of conflicting needs. Cars are now computers on wheels, and while I'd love to drive a car I personally modded at firmware level, I would also be against allowing such cars on public roads. One, hackers make mistakes, and two, malicious actors would trick regular people into modding their cars to further their malicious goals. Both reasons create public hazard. Which is obvious in case of cars, but less obvious with computers connected to the Internet.
At this point I fear we might need to fork computing entirely - let the regular users live in "hell" of propertiary, locked down services they don't actually own, while ourselves, we get the "heaven" of free software... that's pretty much not allowed to interact with regular users. I don't see how to keep the two worlds as one, because all features meant for hackers can also be used by malicious actors to pwn people.
Consider e.g. dev console in a web browser. All is cool, because regular users don't know what F12 does and wouldn't even think of pressing it. But then Facebook and others have to put Self-XSS measures into place, because a malicious actor can tell a regular user what F12 does, and how it "can" let them see who viewed their Facebook profile...
I hate the idea of split world. It means I won't be able to e.g. automate my banking or pizza delivery, because those things will have to go through "dumb" computing, to avoid self-pwnage risks. It means that eventually I won't be able to even get a general-purpose computer, because the nature of niche markets is that they generally don't get served with good stuff at accessible prices - they either get served at exorbitant prices, or don't get served at all.
So I don't want that split world. I want an alternative to fight for. But as I previously wrote, I can't see any.