As a friend of Mike, a former Scaled Engineer, and one that was directly involved in a previous Scaled accident, I have to completely disagree with your statements.
The culture at Scaled has been and will continue to be focused on nothing but safety. This was the first flight accident that Scaled ever had in its existence since 1982, with dozens of first flights of new aircraft designs and hundreds of follow up test flights. There had been engineering mistakes on many flights previously (I certainly made some), but the safety culture that Burt Rutan instilled in everyone focusing on "Question, Never Defend" was prevalent and always managed to get the aircraft home. The report mentions that no one ever thought about what would happen if a pilot pulled the unlock lever early. I guarantee you, everyone did. But just like a pilot knows not to put the gear down above max gear speed, or do full control movements when faster than the max maneuvering speed because things will break (and there are no interlocks on those things either), it could easily be expected that a pilot would never throw the feather unlock except when they are supposed to. Test pilots fly the test card and nothing but the test card. They are highly trained to follow the procedure on the test card. I'm certain Mike did that card over and over on the simulator and threw the feather unlock at the Mach 1.4 callout correctly every time. For some reason he uncharacteristically did the steps out of order on this flight. The result was catastrophic.
Your analogies don't hold up. If I'm in a car at 60mph and I turn a little too early, directly into a tree instead of on to a highway exit ramp, it can be pretty catastrophic to the car and its occupants. Until our autonomous cars show up, you can't design out the steering wheel. If you don't have time to look at the checklist for your next step because of the environment or because the workload is high and your muscle memory fails and you end up doing steps a little too early, it might also be catastrophic. If the procedure or checklist isn't followed exactly, catastrophic things can happen even on highly automated airlines.
Similarly, since a car's crumple zone, seat belt or airbag probably won't save an occupant that crashes into a tree at 200mph (lets up the speed since Mach 1+ is quite a bit higher than most average planes), you can probably understand that at certain speeds, you can't design in similar safety systems. This is called tradeoff analysis and is part of engineering, not malpractice.