In other words: does "bullshit-free computing experience" (or let's just say usability) have to exclude freedom (i.e. your options to freely modify hardware/software you own/use)? I'm thinking about that for some time and I think that (as most of the things) it's not a objective thing but dependend on the philosophy of the producer/maker. And I'm sure that there are people who want to produce well designed things (be that a phone or an app) that can be modified by users/owners (here comes the topic of ownership in the light of digital world, but that's another thing).
And to continue the car analogy, lots of car modifications are illegal for safety and public health (smog) reasons. I think computers are headed in the same direction in the next 40-50 years. The children of tomorrow will think it's absolutely bananas that we used to run unsigned code, because malware behaves much like pollution.
Your car analogy can provide insight into the consequences of a single insecure system in the network, but at the same time it's not valid when you consider that you can (should) control your systems and network if it has to fit your needs.