I'm not saying things
couldn't work differently, only that the incentives don't align to make that very easy to accomplish. Tesla did it because they had the advantage of looking at the current status quo and saying "Yeah, no thanks, we'll retain control of whole process."
I get what you mean about certain aspects, but I would not describe the process of buying a car in that way.
I don't know what you mean. I don't think I said much about the hassle of buying a car: I agree with you on that. When I say "service is the key" I mean mechanically servicing the car, not customer service.
I also wouldn't contradict you on the test drive idea, but that's almost exactly how dealerships do it already. Unless you really insist on driving the exact car you're buying, they are going to direct you towards the demo car reserved for that purpose.
Repair shops: Yes they can exist outside of dealerships, but manufacturers can't build their own service centers without bankrupting the dealerships, which is how they get sales in the first place. Dealerships do occasionally flip to another manufacturer if the local market for their cars is bad, and they would do that in a heart beat if the manufacturer opened its own independent service center nearby.
I completely agree that better models for all of this could exist, but, as you said, the intertwining factors are a real rats nest. This is why I'm extremely skeptical when someone claims everything will be different in 20 years. Breaking this rats nest requires some type of black swan event. By definition those are mostly unforeseeable, and I don't see anything right now to change things. Carvana and those like it focus on used cars, which have always been much more decoupled from the manufacturer/dealership relationship already.
As a final side note, you can avoid the 4-hour dealership visit pretty easily these days: My wife just needed a new car, and we worked with their online sales person via email, casually going back & forth 2 or 3 times over the course of a discussing options and hammering out the details. Trade-in value was determined by giving them the VIN # and pictures of the car. When we went in to pick up the car, all we had to do was review the details. There was a little bit of wait for the insurance company to put the car on our policy (they can't do that until the transaction is official) and for the finance officer to be available, after which we reviewed the paper work, signed, and were done. The whole process took under an hour.