It all comes down how much you want to invest for being as safe as possible from accidents. Cost of cargo ship or plane accident is very high and there is no valuable reasons(?) why everyone should be able to drive those vehicles. Therefore it makes sense that those vehicles are driven by professionals and are designed for professionals.
If your server has millions of users and it provide such value that down time is not an options, maintaining such server should be done by professionals and maintenance tools should be designed for professionals.
However thats not case for every server and cost of failing "empty" server is basicly zero (unlike empty cargo plane).
I think it would be interesting to see software designed around not centralized servers, not PCs, but PSs = Personal Servers where user data lives on their own servers and services only link and communicate between them.
> Edit: Brainstorming here: specifically, I'd like a more accessible UI, automatic updates, sensible defaults on all apps, an easier way to get started and so on.
To some degree, that's sort of like saying "I can drive a car, and cards are simple, why isn't driving an 18-wheeler truck as simple, or a cargo ship, or a cargo plane? I don't see why it has to be more complicated than a car."